py3: catch TypeError during template operations
Two places in this code Python 3 changed from raising ValueError
to TypeError. So catch the addition exceptions.
IMO this code might be better off performing type sniffing. But
I'm not sure the implications of changing that.
Differential Revision: https://phab.mercurial-scm.org/D2156
#
# Avoid interference from actual test env:
unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL