Clarify why convention tests are failing

[khellang]

Related to #907

The failing test yields:

Expected: True
Actual: False

Now it will include the offending members, which IMO is much more helpful:

Model type 'Octokit.RepositoryContent' contains the following mutable properties:
EncodedContent

[khellang]

Ugh. That didn't work so well...

[00:00:00] Build started
[00:00:02] git config --global core.autocrlf input
[00:00:02] git clone -q https://github.com/octokit/octokit.net.git C:\projects\octokit-net
[00:02:32] fatal: early EOF
[00:02:32] fatal: The remote end hung up unexpectedly
[00:02:32] fatal: index-pack failed
[00:02:32] error: RPC failed; result=18, HTTP code = 200
[00:02:32] Command exited with code 128

[haacked]

Thanks!