Dispatcher: handle worker errors

[maikia]

The dispatcher gets some unhandled errors when running the worker and it breaks
this is to ensure that the dispatcher does not break

Reference Issue

What does this implement/fix? Explain your changes.

Any other comments?

[codecov]

Codecov Report

Merging #465 (d7abe59) into master (9565765) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #465      +/-   ##
==========================================
+ Coverage   93.37%   93.44%   +0.06%     
==========================================
  Files          99       99              
  Lines        8337     8355      +18     
==========================================
+ Hits         7785     7807      +22     
+ Misses        552      548       -4     

Impacted Files	Coverage Δ
ramp-engine/ramp_engine/dispatcher.py	98.11% <100.00%> (+2.57%)	⬆️
ramp-engine/ramp_engine/tests/test_dispatcher.py	100.00% <100.00%> (ø)

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[rth]

This is great, thank you @maikia !

I also run into issues of dispatcher stopping due to unhandled exception in the past.