The script `tools/mcuboot/imgtool/main.py` imports the python packages
`click` and `cryptography` to create the target `pinetime-mcuboot-app`.
Add it tothe build instructions, as it was not installed on my system.
6f9f0e8b0e/tools/mcuboot/imgtool/main.py (L19)6f9f0e8b0e/tools/mcuboot/imgtool/keys/__init__.py (L19)
Also add the commands to install the python requirements into a python
venv virtual environment.