Workaround:
The shader creation problem completely vanishes when importing PyOpenGL additionally to PyQt. It doesn't even matter if it's imported before or after PyQt, just before the first shader is created.
When I add:
from OpenGL import GL
the example from my first post works.
Someone from the PyQt mailing list suggested that this is caused by an error when python dynamically loads the GL library.
Workaround:
The shader creation problem completely vanishes when importing PyOpenGL additionally to PyQt. It doesn't even matter if it's imported before or after PyQt, just before the first shader is created.
When I add:
from OpenGL import GL
the example from my first post works.
Someone from the PyQt mailing list suggested that this is caused by an error when python dynamically loads the GL library.