importlib.import_module() include the name of the module when the
'package' argument is missing but needed.

Patch by Neil Schemenauer, minimally modified.

(re-apply after fix for tkinter-related crash)

(issue #15721)

docstrings and ValueError messages. Patch by Zhongyue Luo

now working with comment block selections. Patch was part of 18226 patch.

Move comment code to a separate function so it can be separately tested.
Original patches by Todd Rovito and Phil Webster.

Before this patch it would raise an error when trying to display
documentation for a method that used annotations.

Patch by Claudiu Popa.