TypeError: execv() arg 2 must contain only strings

[Ryan J Ollos]

From the logs:

[pid 7564 139730844530432] 2016-03-14 16:05:09,876 Trac[main] ERROR: Internal Server Error: <RequestWithSession "GET '/changeset?new=302bd3796163449f419a328fb5ce566b6cc55948@/&old=14519%2540/<%00ScRiPt%20%0d%0a>prompt(937841)</ScRiPt>&reponame=psuter.git&sfph_mail=&sfp_email=sample@email.tst'">, referrer 'http://trac.edgewall.org/'
Traceback (most recent call last):
  File "/usr/local/virtualenv/1.1dev/lib/python2.7/site-packages/trac/web/main.py", line 607, in _dispatch_request
    dispatcher.dispatch(req)
  File "/usr/local/virtualenv/1.1dev/lib/python2.7/site-packages/trac/web/main.py", line 256, in dispatch
    resp = chosen_handler.process_request(req)
  File "/usr/local/virtualenv/1.1dev/lib/python2.7/site-packages/trac/versioncontrol/web_ui/changeset.py", line 256, in process_request
    old = repos.normalize_rev(old or new)
  File "/usr/local/virtualenv/1.1dev/lib/python2.7/site-packages/tracopt/versioncontrol/git/git_fs.py", line 534, in normalize_rev
    normrev = self.git.verifyrev(rev)
  File "/usr/local/virtualenv/1.1dev/lib/python2.7/site-packages/tracopt/versioncontrol/git/PyGIT.py", line 717, in verifyrev
    rc = self.repo.rev_parse('--verify', rev).strip()
  File "/usr/local/virtualenv/1.1dev/lib/python2.7/site-packages/tracopt/versioncontrol/git/PyGIT.py", line 139, in __execute
    p = self.__pipe(git_cmd, stdout=PIPE, stderr=PIPE, *cmd_args)
  File "/usr/local/virtualenv/1.1dev/lib/python2.7/site-packages/tracopt/versioncontrol/git/PyGIT.py", line 132, in __pipe
    close_fds=close_fds, **kw)
  File "/usr/lib/python2.7/subprocess.py", line 710, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1335, in _execute_child
    raise child_exception
TypeError: execv() arg 2 must contain only strings

This looks to be similar to #11291.