Fix syntax

conda/clean-betas.py

@@ -70,7 +70,7 @@ def main(scandir, dry_run):
     for f in filenames:
       if f.startswith('repodata.json'): continue
       m = package_regex.match(f)
-      if is None:
+      if m is None:
         print('ignoring `%s\' (does not match)' % os.path.join(path, f))
         continue