hgdemandimport: bypass demandimport for _ast module (
issue6407)
This is broken on Python 3.9rc1, and while it sounds like there may be
a fix in Python, we probably also should have this workaround in place
in hg. See the bug for more details (including on bugs at redhat and
b.p.o).
Differential Revision: https://phab.mercurial-scm.org/D9004
#
# Avoid interference from actual test env:
unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL