fix linting issues

[codecov[bot]]

Codecov Report

Merging #526 (c09296f) into master (8db9f48) will increase coverage by 0.00%. The diff coverage is 75.00%.

@@           Coverage Diff           @@
##           master     #526   +/-   ##
=======================================
  Coverage   84.26%   84.26%           
=======================================
  Files          78       78           
  Lines       16834    16836    +2     
  Branches     2559     2559           
=======================================
+ Hits        14185    14187    +2     
  Misses       1952     1952           
  Partials      697      697           

Impacted Files	Coverage Δ
weaver/processes/utils.py	80.66% <ø> (ø)
weaver/utils.py	84.19% <0.00%> (ø)
weaver/datatype.py	78.48% <66.66%> (+0.01%)	:arrow_up:
weaver/processes/convert.py	83.57% <100.00%> (+0.01%)	:arrow_up:
weaver/processes/wps_package.py	83.19% <100.00%> (ø)
weaver/xml_util.py	100.00% <100.00%> (ø)

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