- httptest, osctest, util.test_cpio: pep8-ified code
- httptest.RequestDataMismatch: enhanced __str__ method

__str__ also returns a unified diff of the expected and actual
value (useful for easier debugging).
- httptest.RequestDataMismatch: removed debugging cruft
- test_remote, test_remote_fixtures: fixed testcases

Recent lxml versions changed the attribute ordering for newly created
nodes: by default the attributes are sorted lexicographically. Thus
the fixtures have to be adapted accordingly.

Consequently, the testsuite will fail with old lxml versions (which
is ok).