It's bad practice to derive custom exception classes from BaseException.

[jfinkhaeuser]

Changes proposed in this pull request:

• Derive from Exception rather than BaseException (see https://www.python.org/dev/peps/pep-0352/)
• Change the expectation that InvalidSpecification is only raised outside debug mode.

Note: the latter change is in line with how exceptions are generally handled in connexion. It'd be easy enough to pass this particular error through anyway.

[coveralls]

Coverage remained the same at 100.0% when pulling f804a96 on jfinkhaeuser:no-base-exception into 52ec049 on zalando:master.

[rafaelcaricio]

👍