tests: fix http-bad-server expected errors for python 3.10 (issue6643)
The format of the error message changed with this version of Python.
This also removes obsolete Python 3 checks.
lib - sys sys
mercurial - sys sys
hgrc.d - sys sys
9diff.rc - sys sys
factotum.rc - sys sys
rc - sys sys
bin - sys sys
9diff - sys sys
hg - sys sys
sys - sys sys
lib - sys sys
python - sys sys
lib - sys sys
python2.5 - sys sys
site-packages - sys sys
hgext - sys sys
+ - sys sys
mercurial - sys sys
+ - sys sys
mercurial-VERSION-py2.5.egg-info - sys sys
src - sys sys
cmd - sys sys
hg - sys sys
+ - sys sys