garbage collected.

Patch by John Mark Vandenberg.

Original patch by John Mark Vandenberg.

whitespace is a substring of smallest leading whitespace.
Based on patch by Robert Li.

whitespace is a substring of smallest leading whitespace.
Based on patch by Robert Li.

Patch by John Mark Vandenberg.

Clarify message and expected action for beginners.
Guard against astral chars in path incorporated in message.

This restores details lost in revision 097f4fda61a4 (since Python 3.3,
related to the new OSError subclasses). Further additions:

* Markup for attributes and constructor signature
* Explain "winerror" and "filename2"
* Extend test to check for filename2 defaulting to None
* Clarify that the constructor can return a subclass

I have intentionally left out any details of allowing more than five
arguments, or how the "args" attribute is set for four or more arguments.
These details seem to be dependent on the Python version and platform.

(tkinter._fix no longer exists in 3.5+)

rather than from elsewhere on PATH.

(by returning the original object unchanged).