update ez_setup.py to latest/last (?) release

Let's see if this helps with #22.

ez_setup.py

@@ -1,18 +1,15 @@
 #!/usr/bin/env python
-"""Bootstrap setuptools installation
 
-To use setuptools in your package's setup.py, include this
-file in the same directory and add this to the top of your setup.py::
-
-    from ez_setup import use_setuptools
-    use_setuptools()
-
-To require a specific version of setuptools, set a download
-mirror, or use an alternate download directory, simply supply
-the appropriate options to ``use_setuptools()``.
-
-This file can also be run as a script to install or upgrade setuptools.
 """
+Setuptools bootstrapping installer.
+
+Maintained at https://github.com/pypa/setuptools/tree/bootstrap.
+
+Run this script to install or upgrade setuptools.
+
+This method is DEPRECATED. Check https://github.com/pypa/setuptools/issues/581 for more details.
+"""
+
 import os
 import shutil
 import sys
@@ -26,16 +23,31 @@ import contextlib
 
 from distutils import log
 
+try:
+    from urllib.request import urlopen
+except ImportError:
+    from urllib2 import urlopen
+
 try:
     from site import USER_SITE
 except ImportError:
     USER_SITE = None
 
-DEFAULT_VERSION = "3.5.1"
-DEFAULT_URL = "https://pypi.python.org/packages/source/s/setuptools/"
+# 33.1.1 is the last version that supports setuptools self upgrade/installation.
+DEFAULT_VERSION = "33.1.1"
+DEFAULT_URL = "https://pypi.io/packages/source/s/setuptools/"
+DEFAULT_SAVE_DIR = os.curdir
+DEFAULT_DEPRECATION_MESSAGE = "ez_setup.py is deprecated and when using it setuptools will be pinned to {0} since it's the last version that supports setuptools self upgrade/installation, check https://github.com/pypa/setuptools/issues/581 for more info; use pip to install setuptools"
+
+MEANINGFUL_INVALID_ZIP_ERR_MSG = 'Maybe {0} is corrupted, delete it and try again.'
+
+log.warn(DEFAULT_DEPRECATION_MESSAGE.format(DEFAULT_VERSION))
+
 
 def _python_cmd(*args):
     """
+    Execute a command.
+
     Return True if the command succeeded.
     """
     args = (sys.executable,) + args
@@ -43,6 +55,7 @@ def _python_cmd(*args):
 
 
 def _install(archive_filename, install_args=()):
+    """Install Setuptools."""
     with archive_context(archive_filename):
         # installing
         log.warn('Installing Setuptools')
@@ -54,6 +67,7 @@ def _install(archive_filename, install_args=()):
 
 
 def _build_egg(egg, archive_filename, to_dir):
+    """Build Setuptools egg."""
     with archive_context(archive_filename):
         # building an egg
         log.warn('Building a Setuptools egg in %s', to_dir)
@@ -64,29 +78,45 @@ def _build_egg(egg, archive_filename, to_dir):
         raise IOError('Could not build the egg.')
 
 
-def get_zip_class():
-    """
-    Supplement ZipFile class to support context manager for Python 2.6
-    """
-    class ContextualZipFile(zipfile.ZipFile):
-        def __enter__(self):
-            return self
-        def __exit__(self, type, value, traceback):
-            self.close
-    return zipfile.ZipFile if hasattr(zipfile.ZipFile, '__exit__') else \
-        ContextualZipFile
+class ContextualZipFile(zipfile.ZipFile):
+
+    """Supplement ZipFile class to support context manager for Python 2.6."""
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, type, value, traceback):
+        self.close()
+
+    def __new__(cls, *args, **kwargs):
+        """Construct a ZipFile or ContextualZipFile as appropriate."""
+        if hasattr(zipfile.ZipFile, '__exit__'):
+            return zipfile.ZipFile(*args, **kwargs)
+        return super(ContextualZipFile, cls).__new__(cls)
 
 
 @contextlib.contextmanager
 def archive_context(filename):
-    # extracting the archive
+    """
+    Unzip filename to a temporary directory, set to the cwd.
+
+    The unzipped target is cleaned up after.
+    """
     tmpdir = tempfile.mkdtemp()
     log.warn('Extracting in %s', tmpdir)
     old_wd = os.getcwd()
     try:
         os.chdir(tmpdir)
-        with get_zip_class()(filename) as archive:
-            archive.extractall()
+        try:
+            with ContextualZipFile(filename) as archive:
+                archive.extractall()
+        except zipfile.BadZipfile as err:
+            if not err.args:
+                err.args = ('', )
+            err.args = err.args + (
+                MEANINGFUL_INVALID_ZIP_ERR_MSG.format(filename),
+            )
+            raise
 
         # going in the directory
         subdir = os.path.join(tmpdir, os.listdir(tmpdir)[0])
@@ -100,58 +130,101 @@ def archive_context(filename):
 
 
 def _do_download(version, download_base, to_dir, download_delay):
-    egg = os.path.join(to_dir, 'setuptools-%s-py%d.%d.egg'
-                       % (version, sys.version_info[0], sys.version_info[1]))
+    """Download Setuptools."""
+    py_desig = 'py{sys.version_info[0]}.{sys.version_info[1]}'.format(sys=sys)
+    tp = 'setuptools-{version}-{py_desig}.egg'
+    egg = os.path.join(to_dir, tp.format(**locals()))
     if not os.path.exists(egg):
         archive = download_setuptools(version, download_base,
-                                      to_dir, download_delay)
+            to_dir, download_delay)
         _build_egg(egg, archive, to_dir)
     sys.path.insert(0, egg)
 
     # Remove previously-imported pkg_resources if present (see
     # https://bitbucket.org/pypa/setuptools/pull-request/7/ for details).
     if 'pkg_resources' in sys.modules:
-        del sys.modules['pkg_resources']
+        _unload_pkg_resources()
 
     import setuptools
     setuptools.bootstrap_install_from = egg
 
 
-def use_setuptools(version=DEFAULT_VERSION, download_base=DEFAULT_URL,
-        to_dir=os.curdir, download_delay=15):
+def use_setuptools(
+        version=DEFAULT_VERSION, download_base=DEFAULT_URL,
+        to_dir=DEFAULT_SAVE_DIR, download_delay=15):
+    """
+    Ensure that a setuptools version is installed.
+
+    Return None. Raise SystemExit if the requested version
+    or later cannot be installed.
+    """
     to_dir = os.path.abspath(to_dir)
+
+    # prior to importing, capture the module state for
+    # representative modules.
     rep_modules = 'pkg_resources', 'setuptools'
     imported = set(sys.modules).intersection(rep_modules)
+
     try:
         import pkg_resources
-    except ImportError:
-        return _do_download(version, download_base, to_dir, download_delay)
-    try:
         pkg_resources.require("setuptools>=" + version)
+        # a suitable version is already installed
         return
+    except ImportError:
+        # pkg_resources not available; setuptools is not installed; download
+        pass
     except pkg_resources.DistributionNotFound:
-        return _do_download(version, download_base, to_dir, download_delay)
+        # no version of setuptools was found; allow download
+        pass
     except pkg_resources.VersionConflict as VC_err:
         if imported:
-            msg = textwrap.dedent("""
-                The required version of setuptools (>={version}) is not available,
-                and can't be installed while this script is running. Please
-                install a more recent version first, using
-                'easy_install -U setuptools'.
+            _conflict_bail(VC_err, version)
 
-                (Currently using {VC_err.args[0]!r})
-                """).format(VC_err=VC_err, version=version)
-            sys.stderr.write(msg)
-            sys.exit(2)
+        # otherwise, unload pkg_resources to allow the downloaded version to
+        #  take precedence.
+        del pkg_resources
+        _unload_pkg_resources()
+
+    return _do_download(version, download_base, to_dir, download_delay)
+
+
+def _conflict_bail(VC_err, version):
+    """
+    Setuptools was imported prior to invocation, so it is
+    unsafe to unload it. Bail out.
+    """
+    conflict_tmpl = textwrap.dedent("""
+        The required version of setuptools (>={version}) is not available,
+        and can't be installed while this script is running. Please
+        install a more recent version first, using
+        'easy_install -U setuptools'.
+
+        (Currently using {VC_err.args[0]!r})
+        """)
+    msg = conflict_tmpl.format(**locals())
+    sys.stderr.write(msg)
+    sys.exit(2)
+
+
+def _unload_pkg_resources():
+    sys.meta_path = [
+        importer
+        for importer in sys.meta_path
+        if importer.__class__.__module__ != 'pkg_resources.extern'
+    ]
+    del_modules = [
+        name for name in sys.modules
+        if name.startswith('pkg_resources')
+    ]
+    for mod_name in del_modules:
+        del sys.modules[mod_name]
 
-        # otherwise, reload ok
-        del pkg_resources, sys.modules['pkg_resources']
-        return _do_download(version, download_base, to_dir, download_delay)
 
 def _clean_check(cmd, target):
     """
-    Run the command to download target. If the command fails, clean up before
-    re-raising the error.
+    Run the command to download target.
+
+    If the command fails, clean up before re-raising the error.
     """
     try:
         subprocess.check_call(cmd)
@@ -160,115 +233,110 @@ def _clean_check(cmd, target):
             os.unlink(target)
         raise
 
+
 def download_file_powershell(url, target):
     """
-    Download the file at url to target using Powershell (which will validate
-    trust). Raise an exception if the command cannot complete.
+    Download the file at url to target using Powershell.
+
+    Powershell will validate trust.
+    Raise an exception if the command cannot complete.
     """
     target = os.path.abspath(target)
+    ps_cmd = (
+        "[System.Net.WebRequest]::DefaultWebProxy.Credentials = "
+        "[System.Net.CredentialCache]::DefaultCredentials; "
+        '(new-object System.Net.WebClient).DownloadFile("%(url)s", "%(target)s")'
+        % locals()
+    )
     cmd = [
         'powershell',
         '-Command',
-        "(new-object System.Net.WebClient).DownloadFile(%(url)r, %(target)r)" % vars(),
+        ps_cmd,
     ]
     _clean_check(cmd, target)
 
+
 def has_powershell():
+    """Determine if Powershell is available."""
     if platform.system() != 'Windows':
         return False
     cmd = ['powershell', '-Command', 'echo test']
-    devnull = open(os.path.devnull, 'wb')
-    try:
+    with open(os.path.devnull, 'wb') as devnull:
         try:
             subprocess.check_call(cmd, stdout=devnull, stderr=devnull)
         except Exception:
             return False
-    finally:
-        devnull.close()
     return True
-
 download_file_powershell.viable = has_powershell
 
+
 def download_file_curl(url, target):
-    cmd = ['curl', url, '--silent', '--output', target]
+    cmd = ['curl', url, '--location', '--silent', '--output', target]
     _clean_check(cmd, target)
 
+
 def has_curl():
     cmd = ['curl', '--version']
-    devnull = open(os.path.devnull, 'wb')
-    try:
+    with open(os.path.devnull, 'wb') as devnull:
         try:
             subprocess.check_call(cmd, stdout=devnull, stderr=devnull)
         except Exception:
             return False
-    finally:
-        devnull.close()
     return True
-
 download_file_curl.viable = has_curl
 
+
 def download_file_wget(url, target):
     cmd = ['wget', url, '--quiet', '--output-document', target]
     _clean_check(cmd, target)
 
+
 def has_wget():
     cmd = ['wget', '--version']
-    devnull = open(os.path.devnull, 'wb')
-    try:
+    with open(os.path.devnull, 'wb') as devnull:
         try:
             subprocess.check_call(cmd, stdout=devnull, stderr=devnull)
         except Exception:
             return False
-    finally:
-        devnull.close()
     return True
-
 download_file_wget.viable = has_wget
 
-def download_file_insecure(url, target):
-    """
-    Use Python to download the file, even though it cannot authenticate the
-    connection.
-    """
-    try:
-        from urllib.request import urlopen
-    except ImportError:
-        from urllib2 import urlopen
-    src = dst = None
-    try:
-        src = urlopen(url)
-        # Read/write all in one block, so we don't create a corrupt file
-        # if the download is interrupted.
-        data = src.read()
-        dst = open(target, "wb")
-        dst.write(data)
-    finally:
-        if src:
-            src.close()
-        if dst:
-            dst.close()
 
+def download_file_insecure(url, target):
+    """Use Python to download the file, without connection authentication."""
+    src = urlopen(url)
+    try:
+        # Read all the data in one block.
+        data = src.read()
+    finally:
+        src.close()
+
+    # Write all the data in one block to avoid creating a partial file.
+    with open(target, "wb") as dst:
+        dst.write(data)
 download_file_insecure.viable = lambda: True
 
+
 def get_best_downloader():
-    downloaders = [
+    downloaders = (
         download_file_powershell,
         download_file_curl,
         download_file_wget,
         download_file_insecure,
-    ]
+    )
+    viable_downloaders = (dl for dl in downloaders if dl.viable())
+    return next(viable_downloaders, None)
 
-    for dl in downloaders:
-        if dl.viable():
-            return dl
 
-def download_setuptools(version=DEFAULT_VERSION, download_base=DEFAULT_URL,
-        to_dir=os.curdir, delay=15, downloader_factory=get_best_downloader):
+def download_setuptools(
+        version=DEFAULT_VERSION, download_base=DEFAULT_URL,
+        to_dir=DEFAULT_SAVE_DIR, delay=15,
+        downloader_factory=get_best_downloader):
     """
-    Download setuptools from a specified location and return its filename
+    Download setuptools from a specified location and return its filename.
 
     `version` should be a valid setuptools version number that is available
-    as an egg for download under the `download_base` URL (which should end
+    as an sdist for download under the `download_base` URL (which should end
     with a '/'). `to_dir` is the directory where the egg will be downloaded.
     `delay` is the number of seconds to pause before an actual download
     attempt.
@@ -287,20 +355,22 @@ def download_setuptools(version=DEFAULT_VERSION, download_base=DEFAULT_URL,
         downloader(url, saveto)
     return os.path.realpath(saveto)
 
+
 def _build_install_args(options):
     """
-    Build the arguments to 'python setup.py install' on the setuptools package
+    Build the arguments to 'python setup.py install' on the setuptools package.
+
+    Returns list of command line arguments.
     """
     return ['--user'] if options.user_install else []
 
+
 def _parse_args():
-    """
-    Parse the command line for options
-    """
+    """Parse the command line for options."""
     parser = optparse.OptionParser()
     parser.add_option(
         '--user', dest='user_install', action='store_true', default=False,
-        help='install in user site package (requires Python 2.6 or later)')
+        help='install in user site package')
     parser.add_option(
         '--download-base', dest='download_base', metavar="URL",
         default=DEFAULT_URL,
@@ -314,18 +384,30 @@ def _parse_args():
         '--version', help="Specify which version to download",
         default=DEFAULT_VERSION,
     )
+    parser.add_option(
+        '--to-dir',
+        help="Directory to save (and re-use) package",
+        default=DEFAULT_SAVE_DIR,
+    )
     options, args = parser.parse_args()
     # positional arguments are ignored
     return options
 
-def main():
-    """Install or upgrade setuptools and EasyInstall"""
-    options = _parse_args()
-    archive = download_setuptools(
+
+def _download_args(options):
+    """Return args for download_setuptools function from cmdline args."""
+    return dict(
         version=options.version,
         download_base=options.download_base,
         downloader_factory=options.downloader_factory,
+        to_dir=options.to_dir,
     )
+
+
+def main():
+    """Install or upgrade setuptools and EasyInstall."""
+    options = _parse_args()
+    archive = download_setuptools(**_download_args(options))
     return _install(archive, _build_install_args(options))
 
 if __name__ == '__main__':