tests: allow for a bonus newline in base64'd email payload

Python 3 adds this newline, which is harmless.

test-patchbomb.t now passes on Python 3.

Differential Revision: https://phab.mercurial-scm.org/D4234

contrib/python3-whitelist

@@ -365,6 +365,7 test-patch-offset.t
 test-patch.t
 test-patchbomb-bookmark.t
 test-patchbomb-tls.t
+test-patchbomb.t
 test-pathconflicts-merge.t
 test-pathconflicts-update.t
 test-pathencode.py

tests/test-patchbomb.t

@@ -439,6 +439,7 with a specific bundle type
   CgZcySARUyA2A2LGZKiZ3Y+Lu786z4z4MWXmsrAZCsqrl1az5y21PMcjpbThzWeXGT+/nutbmvvz
   zXYS3BoGxdrJDIYmlimJJiZpRokmqYYmaSYWFknmSSkmhqbmliamiZYWxuYmBhbJBgZcUBNZQe5K
   Epm7xF/LT+RLx/a9juFTomaYO/Rgsx4rwBN+IMCUDLOKAQBrsmti
+   (?)
   --===============*==-- (glob)
 
 utf-8 patch: