Fix/investigate travis failure

[andhus]

Travis failing although tests pass locally.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@e8e6b1c). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master       #1   +/-   ##
=========================================
  Coverage          ?   95.95%           
=========================================
  Files             ?        2           
  Lines             ?      272           
  Branches          ?       54           
=========================================
  Hits              ?      261           
  Misses            ?        9           
  Partials          ?        2

Impacted Files	Coverage Δ
src/scantree/__init__.py	96.85% <100%> (ø)

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