feat(dask): dask check resources

[Alputer]

closes #703

[codecov]

Codecov Report

Attention: Patch coverage is 60.78431% with 20 lines in your changes missing coverage. Please review.

Project coverage is 60.01%. Comparing base (50495fc) to head (ac29ea5).
Report is 23 commits behind head on master.

Files with missing lines	Patch %	Lines
reana_server/validation.py	35.00%	13 Missing ⚠️
reana_server/rest/info.py	56.25%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #704      +/-   ##
==========================================
- Coverage   60.01%   60.01%   -0.01%     
==========================================
  Files          32       32              
  Lines        3509     3559      +50     
==========================================
+ Hits         2106     2136      +30     
- Misses       1403     1423      +20     

Files with missing lines	Coverage Δ
reana_server/config.py	84.32% <100.00%> (+1.28%)	⬆️
reana_server/rest/workflows.py	51.13% <100.00%> (+0.09%)	⬆️
reana_server/rest/info.py	75.00% <56.25%> (-8.34%)	⬇️
reana_server/validation.py	66.66% <35.00%> (-9.81%)	⬇️

[Alputer]

This pull request became unnecessary after we changed the reana.yaml schema to ask for the number of workers for Dask clusters directly. If it is not provided, default value is used which is nonzero. Therefore, the case where users request too few resources so that no worker can be created with the given amount is no longer possible. Therefore closing the pr.