So, python was crashing when I would try and run the following command from the .....\PYTHON_SERVICES\Scripts directory :
"pip install <insert_python_package_name_here> "
This was on a virtual machine ( on VMWare Workstation 16 Pro ) running Windows 2016 server ( OS fully patched ) and had SQL Server 2017 with CU14. Python version at SQL 2017 CU14 level is 3.5.2.
When I ran "pip install...." , python would crash with a message :
"An unhandled win 32 exception occurred in python.exe ....."
Other times I would get a value of  and it would change each time etc.
However the problem is now solved - I can now install python packages fine - my new 2020 Dell Inspirion 5593 with latest Intel 10th Generation i7 CPU is running Windows 10 and has VMWare Workstation 16 Pro on it. The VM I was doing this work in has Win2016 with SQL 2017, was running was at Virtual Machine Hardware Compatibility of 16.x
It appears that Windows 2016 doesn't like that 16.x hardware compatibility level.
So in VMWare Workstation 16 Pro you have these hardware compatibility choices ( in this order ) :
Workstation 5.x, 6.0, 6.5-7.x, 8.x, 9.x, 10.x, 11.x, 12.x, ESXi 6.5 ( same as my ESXi server at home ), 14.x, ESXi 6.7, 15.x , ESXi 7.0, 16.x
Now with ESXI 6.5 hardware compatibility setting enabled for my VM and using BIOS ( not UEFI ), I can run "pip install...." commands from the command prompt and it works happily every time.
How I worked this out was that on my old Dell 2950 VMware server at home ( which is ESXi 6.5 ) - the pip installs worked.
Hopefully this might help someone else.
( As a side note and not related to this issue - if you install CU22 on SQL Server 2017, the CU22 installs python 3.7 ( side by side with 3.5.2), and when you run "pip install....." python package installs for this version works fine - maybe the python.exe for 3.7 is a better version? )