Raise and catch warnings or handle logging

[benoitbryon]

Currently, hospital is binary: pass or fail.
Sometimes information is not blocker, so we do not want an error, but a warning.

As an example, while I check for example.com availability, I want a failure if it does not return HTTP 200 within 1 second. But I want a warning if it is "slow" i.e. if answer was received in more than 0.5 second.

See:

• https://docs.djangoproject.com/en/dev/ref/checks/
• http://docs.python.org/3/library/warnings.html
• http://docs.python.org/3/library/logging.html

[benoitbryon]

Perhaps using logging would be smarter than using exeptions for that purpose:

• While running the healthchecks, catch AssertionError and convert them into logger.error()
• Healthchecks may log warnings, debug or info too.
• The healthcheck view (CLI or WSGI) displays the logs.
• The healthcheck view (CLI or WSGI) returns success if there is no log of level error/critical. It returns failure if there are logs of level error/critical.