Grounding with context fails in Python 3.6

[GrossTor]

Hello,
I am facing a RuntimeError that is produced while working with the clingo Python API. Using previous clingo versions and Python 2, I was able to define a class, pass it to grounding via the named argument "context", and thereby use its methods from within a logic program through the @-syntax. Once I updated to clingo 5.2.1 and Python 3.6 this fails with a RuntimeError.
Here is a toy example of the problem.

import clingo
import sys
print(clingo.__version__)
print(sys.version)

def on_model(m):
    print(m)

class context_provider:
    def ausgeber(self,x):
        print('function call:',x)
        return clingo.Number(2)

context=context_provider()
prg=clingo.Control(['-n0'])
prg.add("base", [], "a(@ausgeber(1)).")
prg.ground([("base", [])],context=context)
prg.solve(on_model=on_model)

Under previous versions, running this Python script would return the expected output:

5.1.0
2.7.11 |Anaconda 2.2.0 (64-bit)| (default, Dec  6 2015, 18:08:32) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)]
('function call:', 1)
a(2)

Under Python 3.6 it no longer works:

5.2.1
3.6.2 |Continuum Analytics, Inc.| (default, Jul 20 2017, 13:51:32) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)]
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
~/Desktop/steady_ready_projects/circuit_enumeration/ASP_files/taking_control/context_function_module.py in <module>()
     20 prg=clingo.Control(['-n0'])
     21 prg.add("base", [], "a(@ausgeber(1)).")
---> 22 prg.ground([("base", [])],context=context)
     23 prg.solve(on_model=on_model)
     24 

RuntimeError: <block>:1:3-15: error: error in context:
  SystemError: Objects/tupleobject.c:81: bad argument to internal function

Is there any way to overcome this problem? Thanks.

Best,
Torsten

[rkaminsk]

This issue should be fixed with 5c67b29. It is already fixed in the master branch. At some point the fix will be included in clingo 5.2.2.

[GrossTor]

I did rebuild the Python library from the current master branch and that solved the problem. Thanks a lot!

Best,
Torsten