Pass errors are not only logged, but also printed again.

[pdamme]

• For a long time, pass errors, which happen inside the DAPHNE compiler, used to be printed to std::cerr.
• Since a recent commit (4a8f003), they are logged using the recently introduced logger, instead.
• Not printing the error messages to std::cerr anymore has at least two significant downsides:
  • Users don't see the error messages anymore. Instead, DaphneDSL scripts may just silently fail.
  • The error output captured by our script-level test cases is useless, since it is empty.
• This commit adds the printing of the error messages to std::cerr again, but also retains the logging of the errors.

[pdamme]

@corepointer Please let me know if there was a good reason to remove the printing of the error messages to std::cerr. I assume it was just a mishap, so I'm merging this myself now :) .

[corepointer]

It was a partial mishap :-P I replaced std::cerr with spdlog::error on purpose but did a bad job in maintaining the expected behavior.

The ultimate goal of our logging facility is to remove these uncontrollable print outs (cout/cerr). I know some of our test cases rely on console output and the default logger configs that I set when merging it in are by far not in a solid state, but since the test cases completed without error when I tested I thought it's good enough for now.

Some things that come to my mind that would improve the situation:

• Better defaults than log level OFF
• a separate named logger that prints to std err and maybe can even avoid being muted by log_level_limit for exceptions and/or script errors
• document when to require std err output

[pdamme]

Fair enough! For those who are interested: See #575 for more on that topic.