Python 3 planning

Which Python 3 version will be targeted? For instance, if f-strings are used, then this will preclude use by Py3 prior to 3.6. Key features by Py3 release:

• fstrings

Desired Python 3 features:

• use of nonlocal
• except exceptiontype as var:

Conversion of examples?

• can be done any time, backward compatibility of examples is not a requirement

Py2 compatibility code to be deleted:

• iterkeys, itervalues, iteritems in ParseResults
• _ustr()
• _MAX_INT
• import compatibility try-excepts
• unicode string literals (u"lskdjjf")