fix travis cov

[diecui1202]

What is the purpose of the change

fix travis code coverage problem

Brief changelog

.travis.yml

Verifying this change

XXXXX

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[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@c6fd684). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #2337   +/-   ##
=========================================
  Coverage          ?   54.78%           
  Complexity        ?     5238           
=========================================
  Files             ?      573           
  Lines             ?    25456           
  Branches          ?     4537           
=========================================
  Hits              ?    13947           
  Misses            ?     9417           
  Partials          ?     2092

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