Patch fetch_db to handle missing 'content-length' header
We don't know why the autopkgtest webserver has stopped providing a
Content-Length header but the current code doesn't handle its absence, so
detect this rather than throwing an exception.
Should be reverted once the header is back, we don't want to be in the dark
about short reads of the db.
Having an entire britney run bail because of a connection reset is a bad
outcome!
Instead, catch this exception and avoid adding the test in question to the
list of queued tests (we can pick it up on the next run).
Possibly we should do more clever handling of a ConnectionResetError such as
reconnecting, but this is a minimum fix that will stop britney from aborting.
8 branches
proposed for merging into this one.
