Create a function for only_strs to help document its purpose.

setuptools/command/easy_install.py

@@ -1334,9 +1334,7 @@ def create_home_path(self):
         if not self.user:
             return
         home = convert_path(os.path.expanduser("~"))
-        for path in self.config_vars.values():
-            if not isinstance(path, str):
-                continue
+        for path in only_strs(self.config_vars.values()):
             if path.startswith(home) and not os.path.isdir(path):
                 self.debug_print("os.makedirs('%s', 0o700)" % path)
                 os.makedirs(path, 0o700)
@@ -2306,6 +2304,13 @@ def current_umask():
     return tmp
 
 
+def only_strs(values):
+    """
+    Exclude non-str values. Ref #3063.
+    """
+    return filter(lambda val: isinstance(val, str), values)
+
+
 class EasyInstallDeprecationWarning(SetuptoolsDeprecationWarning):
     """
     Warning for EasyInstall deprecations, bypassing suppression.