make generate-tests fails for earlgrey out of the box

[hzeller]

On a default install with all the dependencies installed mentioned in the README, make generate-tests will fail, specifically:

$ make generate-earlgrey 
./generators/earlgrey earlgrey
Traceback (most recent call last):
  File "./generators/earlgrey", line 42, in <module>
    subprocess.call(
  File "/usr/lib/python3.8/subprocess.py", line 340, in call
    with Popen(*popenargs, **kwargs) as p:
  File "/usr/lib/python3.8/subprocess.py", line 854, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "/usr/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: 'fusesoc'
make: *** [Makefile:138: generate-earlgrey] Error 1

Reason is, that there are a few requirements that need to be installed; after doing that with

pip3 install --user -r ./third_party/cores/opentitan/python-requirements.txt

The above make generate-earlgrey call works without errors.

Getting these requirements should be part of the ./generators/earlgrey script. Is it possible for the script to install these dependencies locally in a scratch area without messing with the users' ~/.local ?
I leave it up to the Python experts how to solve this best.

[tgorochowik]

Using a scratch area is a good idea (I guess we will have to use virtualenv for that), but I think that expanding the README is a good first step - the fusesoc dependency is included in our requirements.txt too (and that's what the CI currently uses).