test_unversion_parent_and_child_renamed_bug_187207 tests fail on Python 2.7

[Martin Packman]

On Python 2.7 each of the five working tree format variations of the test for bug 187207 error.

<http://babune.ladeuil.net:24842/job/selftest-maverick/37/testReport/junit/bzrlib.tests.per_workingtree.test_unversion/TestUnversion/test_unversion_parent_and_child_renamed_bug_187207_WorkingTreeFormat6_/>

Traceback (most recent call last):
  File "/home/babune/lib/python/testtools/runtest.py", line 144, in _run_user
    return fn(*args)
  File "/home/babune/lib/python/testtools/testcase.py", line 465, in _run_test_method
    testMethod()
  File "/home/babune/babune/slaves/maverick64.local/workspace/selftest-maverick/bzrlib/tests/per_workingtree/test_unversion.py", line 45, in test_unversion_parent_and_child_renamed_bug_187207
    tree = self.make_branch_and_tree(['.'])
  File "/home/babune/babune/slaves/maverick64.local/workspace/selftest-maverick/bzrlib/tests/per_workingtree/__init__.py", line 56, in make_branch_and_tree
    made_control = self.make_bzrdir(relpath, format=format)
  File "/home/babune/babune/slaves/maverick64.local/workspace/selftest-maverick/bzrlib/tests/per_controldir/__init__.py", line 74, in make_bzrdir
    relpath, format=format)
  File "/home/babune/babune/slaves/maverick64.local/workspace/selftest-maverick/bzrlib/tests/__init__.py", line 2345, in make_bzrdir
    maybe_a_url = self.get_url(relpath)
  File "/home/babune/babune/slaves/maverick64.local/workspace/selftest-maverick/bzrlib/tests/__init__.py", line 2261, in get_url
    return self._adjust_url(base, relpath)
  File "/home/babune/babune/slaves/maverick64.local/workspace/selftest-maverick/bzrlib/tests/__init__.py", line 2249, in _adjust_url
    base += urlutils.escape(relpath)
  File "/home/babune/babune/slaves/maverick64.local/workspace/selftest-maverick/bzrlib/urlutils.py", line 69, in escape
    return str(urllib.quote(relpath, safe='/~'))
  File "/usr/lib/python2.7/urllib.py", line 1231, in quote
    if not s.rstrip(safe):
AttributeError: 'list' object has no attribute 'rstrip'

Revision that introduced the incompatibility is <http://svn.python.org/view?view=rev&revision=81265> which was aimed at improving performance <http://bugs.python.org/issue1285086>. As a side effect though, urllib.quote needs an actual string object, not just something to iterate over. The bug is our confusion of make_branch_and_tree with build_tree, but were it not for Barry Warsaw being tough would have started failing on 2.6.6 as well.