adding import error in cmtk.nbs and imprve KeyError when specific att…

[djarecka]

…ributes of edges are required; adding simple tests

should solve some of the issues described here

[codecov-io]

Codecov Report

Merging #2243 into master will decrease coverage by <.01%.
The diff coverage is 69.38%.

@@            Coverage Diff             @@
##           master    #2243      +/-   ##
==========================================
- Coverage   72.32%   72.31%   -0.01%     
==========================================
  Files        1182     1183       +1     
  Lines       58951    58999      +48     
  Branches     8486     8489       +3     
==========================================
+ Hits        42636    42668      +32     
- Misses      14931    14946      +15     
- Partials     1384     1385       +1

Flag	Coverage Δ
#smoketests	72.31% <69.38%> (-0.01%)	⬇️
#unittests	69.89% <69.38%> (-0.02%)	⬇️

Impacted Files	Coverage Δ
nipype/interfaces/cmtk/nbs.py	35.71% <16.66%> (-0.85%)	⬇️
nipype/interfaces/cmtk/tests/test_nbs.py	76.74% <76.74%> (ø)
nipype/pipeline/plugins/multiproc.py	76.76% <0%> (-1.41%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e4e95f3...a28eff5. Read the comment docs.