Invalid symmetric difference expression

[atarkowska]

$ /home/omero/.local/bin/scc merge develop --no-ask --reset --shallow -v -S success-only --push develop_merge_trigger
...
13:11:31 2019-01-31 13:11:31,705 [     scc.git] DEBUG Calling 'git diff --name-only HEAD...65aead19a071e6359e1056e8b860f80f11865494'
13:11:31 2019-01-31 13:11:31,713 [   scc.merge] DEBUG Cleaning remote branches created for merging
13:11:31 2019-01-31 13:11:31,713 [     scc.git] DEBUG Calling 'git remote'
13:11:31 2019-01-31 13:11:31,717 [     scc.git] WARNI Repository missing: olatarkowska
13:11:31 2019-01-31 13:11:31,717 [     scc.git] DEBUG Calling 'git remote rm merge_manics'
13:11:31 2019-01-31 13:11:31,748 [     scc.git] DEBUG Calling 'git remote rm merge_joshmoore'
13:11:31 2019-01-31 13:11:31,791 [     scc.git] DEBUG Calling 'git remote rm merge_will-moore'
13:11:31 2019-01-31 13:11:31,831 [     scc.git] DEBUG Calling 'git remote rm merge_kouichi-c-nakamura'
13:11:31 Traceback (most recent call last):
13:11:31   File "/home/omero/.local/lib/python2.7/site-packages/scc/main.py", line 80, in entry_point
13:11:31     (UpdateSubmodules.NAME, UpdateSubmodules),
13:11:31   File "/home/omero/.local/lib/python2.7/site-packages/yaclifw/framework.py", line 188, in main
13:11:31     ns.func(ns)
13:11:31   File "/home/omero/.local/lib/python2.7/site-packages/scc/git.py", line 3180, in __call__
13:11:31     self.merge(args, self.main_repo)
13:11:31   File "/home/omero/.local/lib/python2.7/site-packages/scc/git.py", line 3210, in merge
13:11:31     set_commit_status=args.set_commit_status)
13:11:31   File "/home/omero/.local/lib/python2.7/site-packages/scc/git.py", line 1793, in rmerge
13:11:31     set_commit_status=set_commit_status)
13:11:31   File "/home/omero/.local/lib/python2.7/site-packages/scc/git.py", line 1523, in merge
13:11:31     files = self.list_merged_files(pullrequest.get_sha())
13:11:31   File "/home/omero/.local/lib/python2.7/site-packages/scc/git.py", line 1423, in list_merged_files
13:11:31     "git", "diff", "--name-only", "%s...%s" % (upstream, sha))
13:11:31   File "/home/omero/.local/lib/python2.7/site-packages/scc/git.py", line 1092, in communicate
13:11:31     raise Exception(msg)
13:11:31 Exception: Failed to run 'git diff --name-only HEAD...65aead19a071e6359e1056e8b860f80f11865494'
13:11:31     rc:     128
13:11:31     stdout: 
13:11:31     stderr: fatal: Invalid symmetric difference expression HEAD...65aead19a071e6359e1056e8b860f80f11865494
13:11:31 
13:11:31 Build step 'Execute shell' marked build as failure
13:11:31 Finished: FAILURE```

[atarkowska]

as @joshmoore pointed to https://twitter.com/brian_d_vaughn/status/958026747928182784?lang=en, looks like one of the contributors branch may be faulty.