Support debugger when installing from source

[davidbrochart]

It looks like installing from source with either pip install . or pip install -e . doesn't install the debugger. I have debugpy installed.
JupyterLab says: "Select a kernel that supports debugging to enable debugger". Any idea?

[davidbrochart]

The kernelspec looks like this:

{
 "argv": [
  "python",
  "-m",
  "ipykernel_launcher",
  "-f",
  "{connection_file}"
 ],
 "display_name": "Python 3 (ipykernel)",
 "language": "python",
 "metadata": {
  "debugger": false
 }
}

Although the value for "debugger" should be:

>>> from ipykernel.debugger import _is_debugpy_available
>>> _is_debugpy_available
True

Any idea @blink1073 @JohanMabille ?

[blink1073]

I believe this is due to the change to the hatch backend. I will take a look.