Raise error if ignore_directives=False but ignore_comments=True

[jwallwork23]

Closes #2839.

I've just been testing out the new ignore_comments and ignore_directives functionality and think it'll be really useful.

However, I noticed that it's possible to set ignore_directives=False with ignore_comments=True, which negates the ignore_directives option choice. Personally, I think this combination should raise an error.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.88%. Comparing base (9b8a0ba) to head (e6aeb10).
Report is 5 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2840   +/-   ##
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  Coverage   99.88%   99.88%           
=======================================
  Files         359      359           
  Lines       50258    50264    +6     
=======================================
+ Hits        50202    50208    +6     
  Misses         56       56           

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[arporter]

Thanks for tidying this up Joe. Just a couple of small things to fix up. I'll run the integration tests in the meantime (although they should be unaffected).

[arporter]

All good now, thanks very much.
Will just have to wait on the integration tests so will be about an hour.

[jwallwork23]

All good now, thanks very much. Will just have to wait on the integration tests so will be about an hour.

Okay great. Thanks for the review @arporter!

[arporter]

The integration tests were (eventually) all green.