writing output file to a specified location.

follow PEP492 change in Py3.5.2 that makes __aiter__() a simple function instead of an async function
See https://bugs.python.org/issue27243

This posed an issue when the type parameter was a typedef.

fix bug where multiple utility code dependencies could be ignored due to loop variable reassignment (only last one wins)

use tuple instead of list for f-string joining because it is faster to allocate - speedup can be up to 20%

we actually know that FormattedValueNode always returns a Unicode string and no other object type => set node type accordingly