planemo finds diff, but does not update the target repo

```
planemo shed_update -t testtoolshed --check_diff

Diffing repository data_manager_bowtie2_index_builder

Attributes do not match: prior_installation_required='False', prior_installation_required=Nonechildren 1 do not match: repositorychildren 1 do not match: packagecd "/var/folders/2z/ntdb9g2n7tq6_bcq4dj9hj9r0000gn/T/tool_shed_diff_pkUSTa"; diff -r _local_ _testtoolshed_

Repository [data_manager_bowtie2_index_builder] not different, skipping upload.
Repository metadata updated.
```

github version: https://github.com/galaxyproject/tools-devteam/blob/master/data_managers/data_manager_bowtie2_index_builder/tool_dependencies.xml

tts repo: https://testtoolshed.g2.bx.psu.edu/view/devteam/data_manager_bowtie2_index_builder/c85369954c54

this happens dozens of times: https://jenkins.galaxyproject.org/view/Tools/job/devteam-TTS-GH-diff/820/testReport/