bug 1244781 - fix unit.sh error when mercurial isn't an old version. r=callek

--HG--
extra : histedit_source : e83e8b1ef9357f7d0fc8c3292cc03407d3b77fe9

testing/mozharness/mozharness/base/vcs/mercurial.py

@@ -513,6 +513,10 @@ class MercurialVCS(ScriptMixin, LogMixin, object):
                                      throw_exception=True)
                 except subprocess.CalledProcessError, e:
                     self.debug("Failed to rebase: %s" % str(e))
+                    # clean up any hanging rebase. ignore errors if we aren't
+                    # in the middle of a rebase.
+                    self.run_command(self.hg + ['rebase', '--abort'],
+                                     cwd=localrepo, success_codes=[0, 255])
                     self.update(localrepo, branch=branch)
                     for r in reversed(new_revs):
                         self.run_command(self.hg + ['strip', '-n', r[REVISION]],