Import fails for branches with regex-special-chars in names

[Saviq]

The branch names in import isn't escaped for regex-special-chars, an example with "++" in the branch name:

Traceback (most recent call last): File "/usr/bin/git-bzr", line 709, in sys.exit(main(sys.argv)) File "/usr/bin/git-bzr", line 703, in main return func(argv[2:]) File "/usr/bin/git-bzr", line 576, in cmd_import if branch_exists(branch): File "/usr/bin/git-bzr", line 107, in branch_exists matcher = re.compile(r'\s%s$' % branch) File "/usr/lib/python2.7/re.py", line 190, in compile return _compile(pattern, flags) File "/usr/lib/python2.7/re.py", line 242, in _compile raise error, v # invalid expression sre_constants.error: multiple repeat