post-receive-fedora-messaging: Don't attempt to decode unicode strings

On Python 3, we can only decode byte sequences.

subprocess.Popen(universal_newlines=True) always returns unicode stdout/sderr.

Fixes https://pagure.io/fedora-infrastructure/issue/9366

Signed-off-by: Miro Hrončok <miro@hroncok.cz>

roles/git/hooks/files/post-receive-fedora-messaging

@@ -51,7 +51,7 @@ def revs_between(head, base):
     if proc.returncode != 0:
         raise IOError('git rev-list failed: %r, err: %r' % (stdout, stderr))
 
-    for line in stdout.decode('utf-8').strip().split('\n'):
+    for line in stdout.strip().split('\n'):
         yield line.strip()