Catch exception raised when parsing

[tiennou]

It seems Clang can arbitrarily raise errors (transient NULL-byte reads from files that exist). Handle those errors by retrying the parsing step 3 times, just in case it goes away.

[carlosmn]

I guess that didn't solve the issue on Ruby 2.6. It's curious that it's happening on that version and seemingly not the others.

[tiennou]

What's really weird is that I'm running ruby 2.6.0p0 (2018-12-25 revision 66547) [x86_64-darwin18], and it doesn't happen at all here. I've been running while [ $? ]; do rake test TESTOPTS="-v --name=test_can_group_functions"; done for a while, and it still hasn't stopped 🙄.