Fix errors reported by flake8 3.6.0

[nsoranzo]

Ignore W503 and W504.

FOR CONTRIBUTOR:

• - I have read the CONTRIBUTING.md document and this tool is appropriate for the tools-iuc repo.
• - License permits unrestricted use (educational + commercial)
• - This PR adds a new tool or tool collection
• - This PR updates an existing tool or tool collection
• - This PR does something else (explain below)

FOR REVIEWER:

• .shed.yml file ok
  • Toolshed user iuc has access to associated toolshed repo(s)
• Indentation is correct (4 spaces)
• Tool version/build ok
• <command/>
  • Text parameters, input and output files 'single quoted'
  • Use of <![CDATA[ ... ]]> tags
  • Parameters of type text or having optional="true" attribute are checked with if str($param) before being used
• Data parameters have a format attribute containing datatypes recognised by Galaxy
• Tests
  • Parameters are reasonably covered
  • Test files are appropriate
• Help
  • Valid restructuredText and uses <![CDATA[ ... ]]> tags
• Complies with other best practice in Best Practices Doc

[nsoranzo]

Tests for qiime_core tools fail because when biom-format package (a dependency of qiime) was moved from bioconda to conda-forge, the pyqi dependency was omitted. To fix that, we need conda-forge/biom-format-feedstock#4 .

Update: I've added pyqi to conda-forge in conda-forge/staged-recipes#6940

[nsoranzo]

Now all qiime_core tests pass for me locally, but time out on Travis.