py3: whitelist test-pull-http.t
There's a lot of work left to do on network-related stuff, but I at
least got one more test passing.
Differential Revision: https://phab.mercurial-scm.org/D2296
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.