See merge request !4

See merge request !5

See merge request !6

Otherwise user might spend a lot of time debugging problem of slapcache-upload
misbehaving.

This gives user the possibility to check what was uploaded to shacache.

Use same option name as libnetworkcache so that config files are compatible

* revive tests (only what was already there)
* `upload` command supports python3
* better log message
* temporary files are removed

See merge request !3

/reviewed-on !2

  ca file is required for work with Python>=2.7.9