Update error handling for file operations

[hackdna]

In get_file_size() and delete_datafile()

[codecov]

Codecov Report

Merging #3041 into develop will decrease coverage by 1.51%.
The diff coverage is 0%.

@@             Coverage Diff             @@
##           develop    #3041      +/-   ##
===========================================
- Coverage    61.19%   59.68%   -1.52%     
===========================================
  Files          433      433              
  Lines        28478    27032    -1446     
  Branches      1288     1275      -13     
===========================================
- Hits         17428    16134    -1294     
+ Misses       11050    10898     -152

Impacted Files	Coverage Δ
refinery/file_store/models.py	81.87% <0%> (-3.25%)	⬇️
refinery/data_set_manager/views.py	60.2% <0%> (-6.54%)	⬇️
refinery/factory_boy/utils.py	98.46% <0%> (-1.14%)	⬇️
refinery/analysis_manager/tasks.py	74.08% <0%> (-1.04%)	⬇️
refinery/ui/source/js/file-browser/ctrls/ctrl.js	30.39% <0%> (-0.38%)	⬇️
refinery/data_set_manager/test_views.py	100% <0%> (ø)	⬆️
refinery/file_store/utils.py	51.57% <0%> (ø)	⬆️

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