Debian stretch/Ubuntu 18.04: Couldn't reach URL / Trust anchors must be non-empty

[raabf]

When you run CommunitiesParser on Debian stretch or Ubuntu 18.04 it could happen that the following error appears:

Couldn't reach URL https://www.peeringdb.com/api/netfac

However the real reason is not displayed in the output. A deeper investigation shows that the real problem is the following:

java.security.InvalidAlgorithmParameterException: the trustAnchors parameter must be non-empty

That again is caused by a malformed local trusted keys store. And the reason why it is malformed is, that Debian stretch and Ubuntu 18.04 generate by default this trusted store in a file format which is only supported by newer versions of java.
It is not something that has to be fixed by CommunitiesParser, but can occur for some users depending on the OS and java version.

The matching bug report is here: https://bugs.launchpad.net/ubuntu/+source/ca-certificates-java/+bug/1739631

A workaround is basically to correctly generate this trusted store manually. There are many posts out there describing this. However a more extended and a good one is here:
https://stackoverflow.com/questions/6784463/error-trustanchors-parameter-must-be-non-empty