Trap all math overflow errors in function block

[tonyforster]

Currently the python function block will give a bad dock visual indication for function=1/0
but for function=log(0) and sqrt(-1), all that happens is that the turtle disappears and an error is logged

can we have a bad dock indication?

[walter]

Probably should trap NameError and ZeroDivisionError too.

[tonyforster]

ZeroDivisionError is OK? print function block (1/0) shows block dock error

[walter]

v97 seems to mostly do the right thing.

[tonyforster]

See also #2314, redundant math. brings in a different library
math.log(0) and math.sqrt(-1) are trapped OK
but
log(0) is not trapped
and
sqrt(-1) returns NAN

[walter]

See explanation in #2314. Should be behaving properly in v99

[walter]

v99 attached should fix #2313, #2314, and #2330

Note that I am printing the error message for Value and Syntax errors since it seems more informative than the stock syntax error graphic, which really applies to the logo code, not the Python code.

[walter]

release candidate 2

[walter]

​http://git.sugarlabs.org/projects/turtleart/repos/mainline/commits/9be2b1e851f836cfd61be16bb9426879dea99f5e

and

​http://git.sugarlabs.org/projects/turtleart/repos/mainline/commits/99915bb76fe3bd593ecf1ad0f5d4170b9db7eb68

address this problem

[tonyforster]

File "/home/olpc/Activities/TurtleArt.activity/TurtleArt/talogo.py", line 855, in myfunction

raise logoerror('#' + str(e))

UnboundLocalError: local variable 'e' referenced before assignment

[walter]

Oops... fixed with ​http://git.sugarlabs.org/projects/turtleart/repos/mainline/commits/60da59ff0a96b996405b7b25e5ccb64dae03d646