mywrite():  The test for trouble in PyOS_vsnprintf was wrong on both ends.  Also, when there is trouble, ensure the buffer has a traiing 0 byte.
mywrite():  The test for trouble in PyOS_vsnprintf was wrong on both
ends.  Also, when there is trouble, ensure the buffer has a traiing
0 byte.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator