sparse: clean up config signature code
Before, 0 was being used as the default signature value and we cast
the int to a string. We also handled I/O exceptions manually.
The new code uses cfs.tryread() so we always feed data into the
hasher. The empty string does hash and and should be suitable
for input into a cache key.
The changes made the code simple enough that the separate checksum
function could be inlined.
from __future__ import absolute_import
import os
if os.environ.get('COVERAGE_PROCESS_START'):
try:
import coverage
import uuid
covpath = os.path.join(os.environ['COVERAGE_DIR'],
'cov.%s' % uuid.uuid1())
cov = coverage.coverage(data_file=covpath, auto_data=True)
cov._warn_no_data = False
cov._warn_unimported_source = False
cov.start()
except ImportError:
pass