typing: add an assertion to mercurial/hgweb/webcommands.py to help pytype I have no idea why this is needed, given the check immediately above. But without it, I'm getting this: File "/mnt/c/Users/Matt/hg/mercurial/hgweb/webcommands.py", line 1164, in filelog: Missing parameter 'toline' in call to function mercurial.dagop.blockdescendants [missing-parameter] Expected: (fctx, fromline, toline) Actually passed: (fctx, fromline) File "/mnt/c/Users/Matt/hg/mercurial/hgweb/webcommands.py", line 1166, in filelog: Missing parameter 'toline' in call to function mercurial.dagop.blockancestors [missing-parameter] Expected: (fctx, fromline, toline, followfirst) Actually passed: (fctx, fromline) Differential Revision: https://phab.mercurial-scm.org/D10211

crecord: null out the curses attribute with `None` on failure to import Pytype got really confused that this could be `Union[module, bool]`, and spewed about tons of attributes that are not available on `bool`. Differential Revision: https://phab.mercurial-scm.org/D10210