Ignore comments in entry point parsing. Fixes #297.

Author: jaraco

CHANGES.rst

@@ -2,6 +2,7 @@ v3.9.1
 ======
 
 * #296: Exclude 'prepare' package.
+* #297: Fix ValueError when entry points contains comments.
 
 v3.9.0
 ======

importlib_metadata/__init__.py

@@ -82,6 +82,7 @@ class Sectioned:
     _sample = textwrap.dedent(
         """
         [sec1]
+        # comments ignored
         a = 1
         b = 2
 
@@ -102,13 +103,17 @@ def __call__(self, line):
 
     @classmethod
     def get_sections(cls, text):
-        lines = filter(None, map(str.strip, text.splitlines()))
+        lines = filter(cls.valid, map(str.strip, text.splitlines()))
         return (
             (section, map(cls.parse_value, values))
             for section, values in itertools.groupby(lines, cls())
             if section is not None
         )
 
+    @staticmethod
+    def valid(line):
+        return line and not line.startswith('#')
+
     @staticmethod
     def parse_value(line):
         return map(str.strip, line.split("=", 1))