bugfix in build_ext: check that ext has an attribute before trying to
use it
 reduces excess cleverness from 1/2 to 1/3
MAINT: Apply 2to3 idioms fixer.

The idioms fixer makes the following replacements.

1) int <- bool
2) comparison or identity of types <- isinstance
3) a.sort() <- sorted(a)

There were two problems that needed to be dealt with after the
application of the fixer. First, the replacement of comparison or
identity of types by isinstance was not always correct.  The isinstance
function returns true for subtypes whereas many of the places where the
fixer made a substitution needed to check for exact type equality.
Second, the sorted function was applied to arrays, but because it treats
them as iterators and constructs a sorted list from the result, that is
the wrong thing to do.

Closes #3062.
Merge pull request #3281 from charris/2to3-apply-idioms-fixer

MAINT: Apply 2to3 idioms fixer.
Merge pull request #3261 from keflavich/f77_ext_bugfix

bugfix in build_ext: check that ext has an attribute before trying to us it