Hello,
documentation (https://docs.python.org/2/library/signal.html) states, that Python by default installs SIGINT handler which cause KeyboardInterrupt. This is not true everytime according to implementation.
"Python installs a small number of signal handlers by default: SIGPIPE ... and SIGINT is translated into a KeyboardInterrupt exception."
It should also mention this "SIGINT is installed only, when default handler is set at startup.". Because user can run python script from non-interative shell as background task and SIGINT handler is not installed, regardless although user does not change Python default behaviour.

Related SO:
http://stackoverflow.com/questions/40775054/capturing-sigint-using-keyboardinterrupt-exception-works-in-terminal-not-in-scr/40785230?noredirect=1

Maybe something like:

> Python installs a small number of signal handlers by default: SIGPIPE is ignored (so write errors on pipes and sockets can be reported as ordinary Python exceptions) and SIGINT (if parent process has not changed it) is translated into a KeyboardInterrupt exception. All of these can be overridden.

That's good.

Proposed as patches but english is not my native language so please review carefully.

New changeset e85ef7a7eacdef2f43e6bf2e67f335100e7ef2da by Julien Palard in branch 'master':
bpo-28795: Signal documentation: Fix misleading statement. (GH-13121)
https://github.com/python/cpython/commit/e85ef7a7eacdef2f43e6bf2e67f335100e7ef2da

Thanks for reporting Jan! It's finally merged \o/

New changeset 721729fca4fab9fd11861844880b3f3780015ae0 by Miss Islington (bot) in branch '3.7':
bpo-28795: Signal documentation: Fix misleading statement. (GH-13121)
https://github.com/python/cpython/commit/721729fca4fab9fd11861844880b3f3780015ae0