This doesn't handle case fo enclosed except blocks, but once again,
sys.exc_info() support is a workaround for software which uses it
instead of properly catching exceptions via variable in except clause.
The implementation is very basic and non-compliant and provided solely for
CPython compatibility. The function itself is bad Python2 heritage, its
usage is discouraged.
This makes exception traceback info self contained (ie doesn't rely on
list object, which was a bit of a hack), reduces code size, and reduces
RAM footprint of exception by eliminating the list object.
Addresses part of issue #1126.
Issue was with uPy: on local machine with micropython-lib installed, io
module is available. Not the case on Travis CI, where only _io module
is available in uPy.
Don't store final, failing value to the loop variable. This fix also
makes for .. range a bit more efficient, as it uses less store/load
pairs for the loop variable.
