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.

Patch by Antoine Pitrou (based on Robin Schreiber's original patch)

 -I

    Run Python in isolated mode. This also implies -E and -s. In isolated mode
    sys.path contains neither the script’s directory nor the user’s
    site-packages directory. All PYTHON* environment variables are ignored,
    too. Further restrictions may be imposed to prevent the user from
    injecting malicious code.