Jupyter jumps out of virtual env to reference different python?

i’m having trouble getting a kernel started under a virtualenv.
i’ve run across this post from May’20
Jupyter Kernel not running same Python version as the Virtual Environment
but still haven’t solved it. (THis is on MacOSX v10.15.) i’ll attach
the full trace below, but the issue seems to be that in the
virtualenv within which i fire up jupyter notebook,
jupyter_client/launcher.launch_kernel() calls a different python?!

the issue must be something in the environment? looking at the
dictionary of values that is the value of cmd (line#132) everything
looks fine, including that PATH has the virtualenv bin directory
first.

looking thru jupyter options, the only ones that point to a particular kernel
to start have python3 as their default. but which python3 also
points to the correct python within the virtualenv.

Anyone have a clue what’s going on, or how to fix it?

Full trace below:


Traceback (most recent call last):
File "/System/Volumes/Data/rikData/virtualenv/covasim/lib/python3.8/site-packages/tornado/web.py", line 1704, in _execute
result = await result
File "/System/Volumes/Data/rikData/virtualenv/covasim/lib/python3.8/site-packages/tornado/gen.py", line 769, in run
yielded = self.gen.throw(*exc_info)  # type: ignore
File "/System/Volumes/Data/rikData/virtualenv/covasim/lib/python3.8/site-packages/notebook/services/sessions/handlers.py", line 69, in post
model = yield maybe_future(
File "/System/Volumes/Data/rikData/virtualenv/covasim/lib/python3.8/site-packages/tornado/gen.py", line 762, in run
value = future.result()
File "/System/Volumes/Data/rikData/virtualenv/covasim/lib/python3.8/site-packages/tornado/gen.py", line 769, in run
yielded = self.gen.throw(*exc_info)  # type: ignore
File "/System/Volumes/Data/rikData/virtualenv/covasim/lib/python3.8/site-packages/notebook/services/sessions/sessionmanager.py", line 98, in create_session
kernel_id = yield self.start_kernel_for_session(session_id, path, name, type, kernel_name)
File "/System/Volumes/Data/rikData/virtualenv/covasim/lib/python3.8/site-packages/tornado/gen.py", line 762, in run
value = future.result()
File "/System/Volumes/Data/rikData/virtualenv/covasim/lib/python3.8/site-packages/tornado/gen.py", line 769, in run
yielded = self.gen.throw(*exc_info)  # type: ignore
File "/System/Volumes/Data/rikData/virtualenv/covasim/lib/python3.8/site-packages/notebook/services/sessions/sessionmanager.py", line 110, in start_kernel_for_session
kernel_id = yield maybe_future(
File "/System/Volumes/Data/rikData/virtualenv/covasim/lib/python3.8/site-packages/tornado/gen.py", line 762, in run
value = future.result()
File "/System/Volumes/Data/rikData/virtualenv/covasim/lib/python3.8/site-packages/notebook/services/kernels/kernelmanager.py", line 176, in start_kernel
kernel_id = await maybe_future(self.pinned_superclass.start_kernel(self, **kwargs))
File "/System/Volumes/Data/rikData/virtualenv/covasim/lib/python3.8/site-packages/jupyter_client/multikernelmanager.py", line 186, in start_kernel
km.start_kernel(**kwargs)
File "/System/Volumes/Data/rikData/virtualenv/covasim/lib/python3.8/site-packages/jupyter_client/manager.py", line 341, in start_kernel
self.kernel = self._launch_kernel(kernel_cmd, **kw)
File "/System/Volumes/Data/rikData/virtualenv/covasim/lib/python3.8/site-packages/jupyter_client/manager.py", line 249, in _launch_kernel
return launch_kernel(kernel_cmd, **kw)
File "/System/Volumes/Data/rikData/virtualenv/covasim/lib/python3.8/site-packages/jupyter_client/launcher.py", line 132, in launch_kernel
proc = Popen(cmd, **kwargs)
File "/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/subprocess.py", line 854, in __init__
self._execute_child(args, executable, preexec_fn, close_fds,
File "/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/subprocess.py", line 1702, in _execute_child
raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: '/usr/local/opt/python/bin/python3.7'