qguv/rpcalc — pull request #4 by qguv (2013-08-15 13:50:47+00:00)
Title: hotfixes: arithmetic error handling

Merged from hotfix to master and develop:
- OverflowError is now handled properly; values are deleted from the
stack.
- Operators can now return a value, which is assigned to an error if it
is not the empty string, None, or '\n'. This fixes arithmetic errors
(can't ln a negative; can't divide by zero).