Problematic loading data with exec

[ikajic]

I had a case where one of the stored parameters was text which Python did not manage to evaluate as an object it recognizes:
_context = <pyopencl.Context at 0x319aaa0 on <pyopencl.Device 'GeForce GTX 970' on 'NVIDIA CUDA' at 0x251dc60>>

this ended up not loading the data (returning [] from Data object) and it took some time to figure it out. I raised the issue because:
a) cases such as these should also be handled somehow
b) it would be useful if an Exception would not continue quietly in this case, even a small warning would be very useful