The key fingerprint should be only hex digits, everything else can be
discarded. That makes it easy to use this function various fingerprint
formats, including the common, human-readable forms spaces between pairs or
quartets.
http://example.org/index-v1.jar now returns the HTTP header
"Content-Encoding: gzip" but then the reply is plain HTML. That
triggers a ContentDecodingError instead of an HTTPError, so this
changes the test to success on any RequestsException.
These were both spamming the output with lots of confusing messages, even
when --verbose was not used. Jarsigner especially has confusing messages,
since it has warnings that do not pertain to APK signatures at all, like
the ones about timestamps and missing Certificate Authority.
closes#405
apksigner v0.7 (build-tools 26.0.1), Google made it require that the
AndroidManifest.xml was present in the archive before it verifies the
signature. So this needs to stick with the jarsigner hack for JARs.
