[MERGE][0.16] temp file for commit message in external editor should be opened in text mode (#110901)

[John Arbash Meinel]

John Arbash Meinel has voted -0.
Status is now: Approved
Comment:
Please wait before merging.
I don't have time to do a full review but there is some cruft in the 
tests.

v-- This is really ugly, and we should find a better way to wrap the 
lines.

+        msgfilename, hasinfo = bzrlib.\
+                               msgeditor.\
+                               _create_temp_file_with_commit_template(
+                                    'infotext', '----', 'start 
message')

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C46364EF6.3040308%40ukr.net%3E