POETRY: Add awareness of pip installed packages

 

Poetry is not aware of accidental/purposeful use of pip to install packages

$ poetry init
$ poetry add tqdm
$ poetry shell
$ pip install numpy # e.g., user did this accidentally 

Actual

$ poetry lock && poetry install
$ poetry show
tqdm 4.50.0 Fast, Extensible Progress Meter

Expected

$ poetry lock && poetry install
$ poetry show
tqdm 4.50.0 Fast, Extensible Progress Meter
numpy 1.19.2 NumPy is the fundamental package for array computing with Python.

I understand this is very difficult to support currently and the current design recommends user to avoid pip in favor of installing via poetry. However, in peculiar cases (e.g., syntax conventions), sometimes install via poetry is not possible/easy and pip is preferred to be used.