update_crate_tests.py: don't use sys.exit()

If the TEST_MAPPING cannot be generated, print the reason, but
exit without error. It's not uncommon for the output of cargo2android
to fail to build e.g. if a new depencency is not satisfied, so we can
fall back to the previous TEST_MAPPING, or run update_crate_tests
locally once all dependencies are present.

Bug: 179132533
Test: tools/external_updater/updater.sh update rust/crates/textwrap
Test: tools/external_updater/updater.sh update rust/crates/libc
Change-Id: I4802c77332d1ab1d6604d48c47365f40bdbd1122
1 file changed