Fix an issue in stdlib path checking.

jedi/evaluate/helpers.py

@@ -13,6 +13,9 @@ def is_stdlib_path(path):
     # Python standard library paths look like this:
     # /usr/lib/python3.5/...
     # TODO The implementation below is probably incorrect and not complete.
+    if 'dist-packages' in path or 'site-packages' in path:
+        return False
+
     base_path = os.path.join(sys.prefix, 'lib', 'python')
     return bool(re.match(re.escape(base_path) + '\d.\d', path))