The trick to getting Ops to execute is where they're installed. The environment variable which Cortex's ClassLoader class uses to find Ops is:

$IECORE_OP_PATHS

This is a colon-delimited path list and under each path the Op must be explicitly versioned and installed in it's own directory according to:

<PATH>/<OP>/<OP>-<VERSION>.py

For example:

myOps/
|-- meshOp
|   `-- meshOp-1.py
`-- imageProcessingOp
    |-- imageProcessingOp-1.py
    `-- imageProcessingOp-2.py

Nesting is also possible:

myOps/
|-- categoryA
|   `-- opA
|       `-- opA-1.py
|   `-- opB
|       `-- opB-1.py
|-- categoryX
|   `-- opM
|       `-- opM-1.py
|   `-- opN
|       `-- opN-1.py