<!-- Verify first that your issue is not already reported. -->
<!-- If possible, test if the latest release is affected too. -->

## Summary

<!-- general description of the problem -->

## Steps to reproduce

 1. 
 2. 
 3. 

<!-- Reporting a minimal example that reproduces the problem in the text of
the issue can increase the chance of a solution significantly. -->

## Actual result

## Expected result

## Environment

<!-- replace the comments with the output of the commands -->

 * Operating system: <!-- uname -a or lsb_release -a: Debian GNU/Linux 9.1 (stretch), Windows 7, Ubuntu Xenial, etc -->
 * Linkchecker version: <!-- linkchecker --version -->
 * Python version: <!-- python --version -->
 * Install method: <!-- distribution package, PyPI, from source tarball, from git, etc -->

## Configuration

<!-- Include the output of `linkchecker -Dcmdline -q -f <FILENAME>` inline, not as an attachment, -->
<!-- you may want to substitute any sensitive strings, make sure any substitutions are consistent -->
<!-- in the reported result and logs. -->
<!-- (if you don't use -f/--config when reproducing the problem omit that option here). -->

## Logs

<!-- The exact command line used -->
<!-- Rerun with -Dall and include all relevant lines -->
<!-- If a Traceback happened include it in full as well -->

## Other notes

<!-- Ideas on what might have caused this or could fix this are welcome of
course. -->
