tests/test-gendoc-pt_BR.t

worker: handle interrupt on windows

After applying suggestions from https://phab.mercurial-scm.org/D1564
to catch all exceptions in the same way I actually broke the handling of
KeyboardInterrupt on windows. The reason is that KeyboardInterrupt doesn't
dervie from Exception, but BaseException:
https://docs.python.org/2/library/exceptions.html starting from python 2.5

Test Plan:
Run hg on windows and ctrl-c during a large update. No random
exceptions from threads surface in the shell. Previously we'd nearly always get
stack traces from some of threads

Run tests ./run-tests.py
[...]
Failed test-convert-svn-encoding.t: output changed
# Ran 622 tests, 41 skipped, 1 failed.
python hash seed: 2962682116

The test failing seems to have nothing to do with the change and fails on base
revision as well

Differential Revision: https://phab.mercurial-scm.org/D1718

#require docutils gettext

  $ $TESTDIR/check-gendoc pt_BR
  checking for parse errors