repo: Remove unused variable in 'except'

Change-Id: I90f89ed6638a3d2a9e665ebbedef5dd7902f5429
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/254695
Reviewed-by: Mike Frysinger <vapier@google.com>
Tested-by: David Pursehouse <dpursehouse@collab.net>

repo

@@ -558,7 +558,7 @@ def SetupGnuPG(quiet):
     proc = subprocess.Popen(cmd,
                             env=env,
                             stdin=subprocess.PIPE)
-  except OSError as e:
+  except OSError:
     if not quiet:
       print('warning: gpg (GnuPG) is not available.', file=sys.stderr)
       print('warning: Installing it is strongly encouraged.', file=sys.stderr)