Python: don't catch KeyboardInterrupt and SystemExit

[Dvad]

What

Currently, the python sdk will catch any exception raised inside a rerun log function and surface it as a printed warning rather than an exception to the client. This makes sense to avoid crashing the app for a mistake in the argument of the log function. This can be disabled with the "strict mode" through an environment variables.

However, there are little reasons to emit a warning and keep-on going when a KeyboardInterrupt exception is received. The official doc states even that this kind of exception are better not being caught at all:

Note Catching a KeyboardInterrupt requires special consideration. Because it can be raised at unpredictable points, it may, in some circumstances, leave the running program in an inconsistent state. It is generally best to allow KeyboardInterrupt to end the program as quickly as possible or avoid raising it entirely. (See Note on Signal Handlers and Exceptions.)

I propose to have a special case for this type of exception, and throwing them back to the client even in non strict mode.

I tested, that Ctrl-C now interrupts some test program instantly instead of being unreliable before (because sometime catches inside rerun log).

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[emilk]

Good catch - thanks for the PR!

[emilk]

I believe this is the better fix - this will ignore both KeyboardInterrupt and SystemExit

Suggested change

	if exc_type is not None and exc_type is not KeyboardInterrupt and not strict_mode():
	if exc_type is Exception and not strict_mode():

[nikolausWest]

If that's the intention, perhaps worth adding a comment to the effect as well?

[abey79]

@emilk well spotted (I had forgotten about that Exception vs. BaseException thing). I fixed the code with the correct issubclass check + a comment.

Changes were made, but needed to unblock merge.