Ignore PyPIClient releases with invalid PEP440 versions

This commit filters all package releases returned by pypi.org, which do not
provide valid PEP440 versions instead of raising invalid version exception.

This is required for libraries such as `pytz` which contain releases with
invalid version schemas such as "2004a", "2004b".

package_control/clients/pypi_client.py

@@ -1,8 +1,8 @@
 import re
 
+from ..pep440 import PEP440InvalidVersionError
 from ..pep440 import PEP440Version
 from ..pep440 import PEP440VersionSpecifier
-from ..package_version import version_sort
 
 from .json_api_client import JSONApiClient
 
@@ -64,6 +64,7 @@ def download_info_from_releases(self, url, asset_templates, tag_prefix=None):
         :param asset_templates:
             A list of tuples of asset template and download_info.
 
+            ```py
             [
                 (
                     "coverage-${version}-cp33-*-win_amd64*.whl",
@@ -73,6 +74,7 @@ def download_info_from_releases(self, url, asset_templates, tag_prefix=None):
                     }
                 )
             ]
+            ```
 
             Supported globs:
 
@@ -192,25 +194,36 @@ def _download_info_from_latest_version(self, name, asset_templates):
         """
 
         pypi_url = "https://pypi.org/pypi/{}/json".format(name)
+
+        # fetch dictionary of form `version: [asset, asset]`
         releases = self.fetch_json(pypi_url)["releases"]
 
+        # create a list of valid pep440 versions
+        versions = []
+        for version in releases:
+            try:
+                versions.append(PEP440Version(version))
+            except PEP440InvalidVersionError:
+                continue
+
         asset_templates = self._expand_asset_variables(asset_templates)
 
         max_releases = self.settings.get("max_releases", 0)
         num_releases = [0] * len(asset_templates)
 
         # get latest compatible release for each asset template
         output = []
-        for version in version_sort(releases, reverse=True):
+        for version in sorted(versions, reverse=True):
             # we don"t want beta releases!
-            if not PEP440Version(version).is_final:
+            if not version.is_final:
                 continue
 
-            assets = releases[version]
+            version_string = str(version)
+            assets = releases[version_string]
             for idx, (pattern, selectors) in enumerate(asset_templates):
                 if max_releases > 0 and num_releases[idx] >= max_releases:
                     continue
-                info = self._make_download_info(pattern, selectors, version, assets)
+                info = self._make_download_info(pattern, selectors, version_string, assets)
                 if not info:
                     continue
                 output.append(info)