Print traceback when encountering errors

[ssiccha]

Uses the new command line option --alwaystrace. This lets GAP also print tracebacks when the break loop is disabled by -T.

This still overwrites the library functions Where, WHERE, and ErrorInner. This can be avoided once there is a central GAP error stream where these functions send their output, see gap-system/gap#1815.

Fixes #38.

[ssiccha]

This needs gap-system/gap#2551 to be merged.

[codecov[bot]]

Codecov Report

Merging #70 into master will decrease coverage by 17.64%. The diff coverage is 2.66%.

@@            Coverage Diff             @@
##           master     #70       +/-   ##
==========================================
- Coverage   61.24%   43.6%   -17.65%     
==========================================
  Files           9       9               
  Lines         836     883       +47     
==========================================
- Hits          512     385      -127     
- Misses        324     498      +174

Impacted Files	Coverage Δ
gap/JupyterError.gi	18.18% <2.66%> (-22.91%)	:arrow_down:
gap/JupyterHelp.gi	0% <0%> (-43.28%)	:arrow_down:
gap/JupyterStream.gi	15% <0%> (-30%)	:arrow_down:
gap/JupyterRenderable.gi	70% <0%> (-20%)	:arrow_down:
gap/JupyterInspection.gi	69.11% <0%> (-16.18%)	:arrow_down:
gap/JupyterUtil.gi	25% <0%> (-3.75%)	:arrow_down:
gap/JupyterKernel.gi	76.79% <0%> (-1.69%)	:arrow_down:

[ssiccha]

I've also added a little hack to let the JupyterKernel stay compatible with GAP 4.9.x versions. This is also relatively ugly, but otherwise JupyterKernel would become unusable until GAP 4.10 is released.

[ssiccha]

Done. Unless gap-system/gap#2551is merged into master the travis checks fail due to some "unbound global variable" syntax warning though.

[ssiccha]

I completely forgot about this pull request. Sorry! I just forgot to retrigger the tests once my patch was merged into the gap master branch...

I removed the compatibility hack for 4.9 and made 4.10 a dependency in the PackageInfo.g file.