Fix macro expansion of _PyErr_OCCURRED(), and make sure to use it in at least one place so as to avoid regressions.

Fix macro expansion of _PyErr_OCCURRED(), and make sure to use it in at least one place so as to avoid regressions.

Ensure that the module is unloaded to be able to run the test more than once,
and to not leak memory.

Closes #1215: document better why it is not a good idea to catch e.g. SIGSEGV and refer to faulthandler.

Patch by Martin Pool.

Use the platform-independent way of calling a script from the shell: "python prog.py", not "prog.py"

Found by Micheal Wells on docs@.

Fix: >= and so on are usually called "comparison operators", not "logical operators". Found by Tom Kalt on docs@.