Update ez_setup.py to the latest upstream revision

Source:
Repo:   git://github.com/pypa/setuptools.git
Branch: bootstrap
Commit: 0c3bf692236350f5c2c2cab5b235e9b6d3518fcb

Notice:
Line 39 remained unchanged, so the default version of setuptools
is still `18.3.2` instead of `LATEST`.

@@ -3,6 +3,8 @@
 """
 Setuptools bootstrapping installer.
 
+Maintained at https://github.com/pypa/setuptools/tree/bootstrap.
+
 Run this script to install or upgrade setuptools.
 """
 
@@ -16,24 +18,30 @@ import subprocess
 import platform
 import textwrap
 import contextlib
-import warnings
+import json
+import codecs
 
 from distutils import log
 
 try:
     from urllib.request import urlopen
+    from urllib.parse import urljoin
 except ImportError:
     from urllib2 import urlopen
+    from urlparse import urljoin
 
 try:
     from site import USER_SITE
 except ImportError:
     USER_SITE = None
 
+LATEST = object()
 DEFAULT_VERSION = "18.3.2"
-DEFAULT_URL = "https://pypi.python.org/packages/source/s/setuptools/"
+DEFAULT_URL = "https://pypi.io/packages/source/s/setuptools/"
 DEFAULT_SAVE_DIR = os.curdir
 
+MEANINGFUL_INVALID_ZIP_ERR_MSG = 'Maybe {0} is corrupted, delete it and try again.'
+
 
 def _python_cmd(*args):
     """
@@ -98,8 +106,16 @@ def archive_context(filename):
     old_wd = os.getcwd()
     try:
         os.chdir(tmpdir)
-        with ContextualZipFile(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])
@@ -114,18 +130,19 @@ def archive_context(filename):
 
 def _do_download(version, download_base, to_dir, download_delay):
     """Download Setuptools."""
-    egg = os.path.join(to_dir, 'setuptools-%s-py%d.%d.egg'
-                       % (version, sys.version_info[0], sys.version_info[1]))
+    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
@@ -140,6 +157,7 @@ def use_setuptools(
     Return None. Raise SystemExit if the requested version
     or later cannot be installed.
     """
+    version = _resolve_version(version)
     to_dir = os.path.abspath(to_dir)
 
     # prior to importing, capture the module state for
@@ -189,6 +207,11 @@ def _conflict_bail(VC_err, version):
 
 
 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')
@@ -222,8 +245,8 @@ def download_file_powershell(url, target):
     ps_cmd = (
         "[System.Net.WebRequest]::DefaultWebProxy.Credentials = "
         "[System.Net.CredentialCache]::DefaultCredentials; "
-        "(new-object System.Net.WebClient).DownloadFile(%(url)r, %(target)r)"
-        % vars()
+        '(new-object System.Net.WebClient).DownloadFile("%(url)s", "%(target)s")'
+        % locals()
     )
     cmd = [
         'powershell',
@@ -248,7 +271,7 @@ 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)
 
 
@@ -321,6 +344,7 @@ def download_setuptools(
     ``downloader_factory`` should be a function taking no arguments and
     returning a function for downloading a URL to a target.
     """
+    version = _resolve_version(version)
     # making sure we use the absolute path
     to_dir = os.path.abspath(to_dir)
     zip_name = "setuptools-%s.zip" % version
@@ -333,6 +357,27 @@ def download_setuptools(
     return os.path.realpath(saveto)
 
 
+def _resolve_version(version):
+    """
+    Resolve LATEST version
+    """
+    if version is not LATEST:
+        return version
+
+    meta_url = urljoin(DEFAULT_URL, '/pypi/setuptools/json')
+    resp = urlopen(meta_url)
+    with contextlib.closing(resp):
+        try:
+            charset = resp.info().get_content_charset()
+        except Exception:
+            # Python 2 compat; assume UTF-8
+            charset = 'UTF-8'
+        reader = codecs.getreader(charset)
+        doc = json.load(reader(resp))
+
+    return str(doc['info']['version'])
+
+
 def _build_install_args(options):
     """
     Build the arguments to 'python setup.py install' on the setuptools package.
@@ -347,7 +392,7 @@ def _parse_args():
     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,
@@ -362,9 +407,9 @@ def _parse_args():
         default=DEFAULT_VERSION,
     )
     parser.add_option(
-    	'--to-dir',
-    	help="Directory to save (and re-use) package",
-    	default=DEFAULT_SAVE_DIR,
+        '--to-dir',
+        help="Directory to save (and re-use) package",
+        default=DEFAULT_SAVE_DIR,
     )
     options, args = parser.parse_args()
     # positional arguments are ignored
@@ -372,13 +417,13 @@ def _parse_args():
 
 
 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,
-	)
+    """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():