Improve test failure message

[sed-i]

A test failure looks like this:

ERROR    interface_tester.interface_test:runner.py:55 Failed check 3: validating schema on scene output: 2 validation errors for ProviderSchema
app -> url
  field required (type=value_error.missing)
app -> ingesters -> 0 -> protocol
  field required (type=value_error.missing)

It could be handy if there also was:

• A link to the schema / doc / test.
• More detailed context. It is not clear from "validation errors for ProviderSchema" what was being tested. Does it mean: "a stand-in requirer was not able to parse what the lib's TracingProvider rendered"?