Issue 3194 - Allow multiple sources for a dependency

ensure_dependencies.py

 #!/usr/bin/env python
 # coding: utf-8
 
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 import sys
 import os
 import posixpath
@@ skipping 136 matching lines @@
   "(.+)$"
 )
 
 # [url@]rev
 source_regexp = re.compile(
   "^(?:(.*)@)?"
   "(.+)$"
 )
 
 def merge_seqs(seq1, seq2):
-  """Return a tuple of any truthy values from the suplied sequences
-
-  (None, 2), (1,)      => (1, 2)
-  None, (1, 2)         => (1, 2)
-  (1, 2), (3, 4)       => (3, 4)
+  """Return a list of any truthy values from the suplied sequences
+
+  (None, 2), (1,)      => [1, 2]
+  None, (1, 2)         => [1, 2]
+  (1, 2), (3, 4)       => [3, 4]
   """
-  return tuple(map(lambda item1, item2: item2 or item1, seq1 or (), seq2 or ()))
+  return map(lambda item1, item2: item2 or item1, seq1 or (), seq2 or ())
 
 def parse_spec(path, line):
   if "=" not in line:
     logging.warning("Invalid line in file %s: %s" % (path, line))
     return None, None
 
   key, value = line.split("=", 1)
   key = key.strip()
   items = value.split()
   if not len(items):
@@ skipping 188 matching lines @@
   args = parser.parse_args()
 
   if args.quiet:
     logging.disable(logging.INFO)
 
   repos = args.repos
   if not len(repos):
     repos = [os.path.dirname(__file__)]
   for repo in repos:
     resolve_deps(repo)