PyCharm break on exception does not work with Theano

Question

I cannot get PyCharm to stop on the line of code where an exception is raised, when I import Theano.

My code:

import theano
raise Exception()

I expect PyCharm debugger to stop on the raise Exception() line, but it throws a RuntimeError and exits the debugger:

Traceback (most recent call last):
Error in sys.excepthook:
Traceback (most recent call last):
  File "/homes/user/Downloads/pycharm-community-4.5.1/helpers/pydev/pydevd_breakpoints.py", line 89, in _excepthook
    _original_excepthook(exctype, value, tb)
  File "/usr/local/lib/python2.7/dist-packages/theano/gof/link.py", line 58, in thunk_hook
    __excepthook(type, value, trace)
  File "/homes/user/Downloads/pycharm-community-4.5.1/helpers/pydev/pydevd_breakpoints.py", line 89, in _excepthook
    _original_excepthook(exctype, value, tb)
  File "/usr/local/lib/python2.7/dist-packages/theano/gof/link.py", line 58, in thunk_hook
    __excepthook(type, value, trace)
  <...>
  File "/usr/local/lib/python2.7/dist-packages/theano/gof/link.py", line 58, in thunk_hook
    __excepthook(type, value, trace)
  File "/homes/user/Downloads/pycharm-community-4.5.1/helpers/pydev/pydevd_breakpoints.py", line 84, in _excepthook
    exception_breakpoint = get_exception_breakpoint(exctype, _handle_exceptions)
  File "/homes/user/Downloads/pycharm-community-4.5.1/helpers/pydev/pydevd_breakpoints.py", line 65, in get_exception_breakpoint
    exception_full_qname = get_exception_full_qname(exctype)
  File "/homes/user/Downloads/pycharm-community-4.5.1/helpers/pydev/pydevd_breakpoints.py", line 53, in get_exception_full_qname
    def get_exception_full_qname(exctype):
RuntimeError: maximum recursion depth exceeded

Original exception was:
Traceback (most recent call last):
  File "/homes/user/Downloads/pycharm-community-4.5.1/helpers/pydev/pydevd.py", line 2357, in <module>
    globals = debugger.run(setup['file'], None, None, is_module)
  File "/homes/user/Downloads/pycharm-community-4.5.1/helpers/pydev/pydevd.py", line 1777, in run
    pydev_imports.execfile(file, globals, locals)  # execute the script
  File "/homes/user/corp/python/projects/n_test.py", line 10, in <module>
    raise Exception()
Exception

Answer 1

One hack is to comment out this line sys.excepthook = thunk_hook in .../lib/python2.7/site-packages/theano/gof/link.py

Answer 2

Looks like a bug in one of the libs (maybe both :^)).

For some reason, theano's and PyCharm's excepthooks both think of the other one as its ancestor.

Add debug printing into both libs at points where sys.excepthook and member variables that point to the previous handler are set to reveal the setting order. Someone appears to be breaking the handler chaining rules.