tf2_py compilation error with Python 3.5

[nwaniek]

The function static PyObject *_allFramesAsDot in tf2_py.cpp is incompatible with Python 3.5, as it invokes PyString_FromString. You can find a (trivial) patch at https://gist.github.com/rochus/aa6d274a349c6aaff692a82fa45af450

[astoeckel]

Can confirm, just ran into this issue while compiling ROS on Fedora 27 in a Python 3 venv. The linked patch fixes the problem for me.

[jacknlliu]

Did anyone run into the issue #259 even with this patch?

[tfoote]

This same logic appears to be exactly the same as the contents of the method stringToPython which you're removing: https://github.com/ros/geometry2/blob/indigo-devel/tf2_py/src/python_compat.h#L17-L24 which is designed to specifically to provide this abstraction between python versions.

inline PyObject *stringToPython(const char *input)
{
#if PY_MAJOR_VERSION >= 3
  return PyUnicode_FromString(input);
#else
  return PyString_FromString(input);
#endif
}

I'd like to see that function updated appropriately if there is an issue with it.

[tfoote]

Since the proposed patch appears redundant and with the help of @allenh1, tf2_py is confirmed to be building with python 3.5 https://gist.github.com/allenh1/3e81e2a6fb28b728dc24416826e99af9 I'm going to close this until there's a reproducible issue.