Crash fix python.mod

[michaelortmann]

Found by: pagzlol
Patch by: michaelortmann
Fixes: #1912

One-line summary:
Crash fix, break on error

Additional description (if needed):

Test cases demonstrating functionality (if applicable):
Before:

.load python
.python eggdrop.parse_tcl_list("{")
[01:23:26] tcl: builtin dcc call: *dcc:python -HQ 1 eggdrop.parse_tcl_list("{")
Python Error: <built-in function parse_tcl_list> returned a result with an exception set
eggdrop.error: Supplied string is not a Tcl list

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
SystemError: <built-in function parse_tcl_list> returned a result with an exception set
[... some seconds later ...]
SIGSEGV

After:
No more crash