Only detect a path as an unpacked egg if it also has an EGG-INFO directory. Fixes #462.

CHANGES.txt

@@ -2,6 +2,13 @@
 CHANGES
 =======
 
+----
+18.6
+----
+
+* Issue #462: Provide a more refined detection of unpacked egg
+  directories, avoiding detecting zc.recipe.egg wheel as an egg.
+
 ----
 18.5
 ----

pkg_resources/__init__.py

@@ -2288,6 +2288,7 @@ def _is_unpacked_egg(path):
     """
     return (
         path.lower().endswith('.egg')
+        and os.path.isdir(os.path.join(path, 'EGG-INFO'))
     )
 
 def _set_parent_ns(packageName):