Pip - Fatal error in launcher: Unable to create process using

 python - Pip - Fatal error in launcher: Unable to create process using '"' - Stack Overflow

This worked for me under Windows 10 x64:

Ensure that the Python directories are in the path, e.g.:

# Edit Environment variables so that variable "path" points to the new location.
# Insert these at the start of the list (or delete other Python directories), as Windows takes the first match it finds.
# Run the program "Edit the System Environment Variables".
# Or see Control Panel under "System Properties".
S:\Research\bin\Python375\Scripts\
S:\Research\bin\Python375\

Then:

python -m pip install --upgrade --force-reinstall pip

In my particular case, the error was caused by shifting the Python directory to a new location.