Bug 1394391 - [tryselect] Split hg implementation of files_changed to a list, r=jhford

This fixes a regression from bug 1384593. I was going to add a test for this, but it would be
a better use of time to fix bug 1185599 and add a test there. We already have vcs tests in other
parts of the tree so consolidating them into a single module is likely easier than standing up
another one-off vcs tester.

MozReview-Commit-ID: E51Tb1qC9Wb

--HG--
extra : rebase_source : f957b1857d162fd229dcef0e87668dd270512cf7

tools/tryselect/vcs.py

@@ -148,7 +148,7 @@ class HgHelper(VCSHelper):
     @property
     def files_changed(self):
         return self.run(['hg', 'log', '-r', '::. and not public()',
-                         '--template', '{join(files, "\n")}\n'])
+                         '--template', '{join(files, "\n")}\n']).splitlines()
 
     @property
     def has_uncommitted_changes(self):