planemo shed_update failing, Connection aborted, BadStatusLine

I've not updated anything on the (Test) ToolShed for a while, so I don't know when this changed but:

```
$ uname
Darwin
$ planemo --version
planemo, version 0.33.0.dev0
$ planemo shed_update -t testtoolshed ~/repositories/galaxy_blast/tools/blast2go/ -m "v0.0.11 Fix parameter help text which was not being displayed"
cd '/Volumes/Hitachi-3TB-mirrored/repositories/galaxy_blast/tools/blast2go' && git rev-parse HEAD
cd '/Volumes/Hitachi-3TB-mirrored/repositories/galaxy_blast/tools/blast2go' && git diff --quiet
Could not update blast2go
('Connection aborted.', BadStatusLine("''",))
Repository metadata updated successfully for repository blast2go.
Failed to update a repository.
```

The blank status line is odd...

Start at the planemo shed_update command and reproduce the reported Test ToolShed failure using the command shown. Trace the request that produces the blank BadStatusLine response, then verify the repository update completes successfully without the connection-aborted error.

Written by the indexing model from the issue text.