Support partial exc_info using logger

[maruno]

In our application we were logging exceptions that have been captured and saved. To enter these we use the tri-tuple exc_info format. The framework we use that captures these exceptions (graphql-core) provides us with the exception information missing the stack. Sentry would log something but totally skip the exception information.

This change checks if all the exc_info is (None, None, None) or tries to parse the partial exc_info, still providing the exception class and message in the Sentry event