fix CodeQL false positive

[juarezr]

This PR has the objective of fixing a false positive in CodeQL analysis.

Changes

1. Fixed a false positive in CodeQL analysis due to printing user/password in a sintetic test.

Checklist

Checklist for for pull requests including new code and/or changes to existing code...

• [x] Code
  • [x] Includes unit tests
  • [ ] New functions have docstrings with examples that can be run with doctest
  • [ ] New functions are included in API docs
  • [ ] Docstrings include notes for any changes to API or behaviour
  • [ ] All changes documented in docs/changes.rst
• [x] Testing
  • [ ] Travis CI passes (unit tests run under Linux)
  • [ ] AppVeyor CI passes (unit tests run under Windows)
  • [ ] Unit test coverage has not decreased (see Coveralls)
• [x] Changes
  • [x] Ready to review
  • [x] Ready to merge

[coveralls]

Coverage decreased (-0.0006%) to 91.816% when pulling c90ff77925e220c2ac7cd3ff860b29a20084f299 on juarezr:fixcodeql into 73059f910cc6ba985d7338d251cc6d86c5faba80 on petl-developers:master.