Adding capnp extension validation check
Adding capnp extension validation check

- To catch odd import problems on Windows

SymbiFlow/pycapnp,SymbiFlow/pycapnp,SymbiFlow/pycapnp,jparyani/pycapnp,SymbiFlow/pycapnp,jparyani/pycapnp,jparyani/pycapnp,jparyani/pycapnp