Recently while running:

pip install pyinstaller

I encountered the following error:

Failed to build pyinstaller
Skipping wheel build for altgraph, due to binaries being disabled for it.
Skipping wheel build for pefile, due to binaries being disabled for it.
ERROR: Could not build wheels for pyinstaller which use PEP 517 and cannot be installed directly

It turns out that Windows Defender (the built in AV in Windows 10) was blocking runw.exe

The real error was a few lines above:

error: could not open 'PyInstaller\bootloader\Windows-32bit\runw.exe': Invalid argument


A quick unblock from Windows Defender and it worked.

Thanks to: https://github.com/pyinstaller/pyinstaller/issues/3813#issuecomment-575319940 for the hint.