Fix the detection of the system environment with custom installer

[sdispater]

After several attempts at fixing this, I think this is the best approach: differentiate the custom Poetry virtual environment – by putting a special file – from standard ones so that there is no confusion about what Poetry needs to do when detecting the system environment.

Resolves #4427
Resolves #4414
Resolves #4369
Resolves #4254

Pull Request Check List

• Added tests for changed code.
• Updated documentation for changed code.

[finswimmer]

If I understand the code correct, it should work if there is only one python interpreter in the environment. But what happens if we have a python2, python3.6, python3.7? python2 will be selected. But we cannot be sure that this is the intended interpreter.

Can we make the following assumptions?:

• in a venv there will be only on interpreter
• in the system env there can be multiple interpreter

If so, we could look for python executables of the format pythonX.Y. If we receive exactly one, take it. If we get multiple, take the one with the same version as poetry is running.

BTW: rstrip() doesn't strip .exe from the end of the string. It removes any of the given character from the end until it hits a character not listed. A trap I run into regularly 😄

[sdispater]

I updated the code to look for the executable of the child environment (if given). Otherwise the previous logic is used.

[sdispater]

Note that I intend to rewrite the environment management at some point but it will be after the release of the 1.2 version.

[datacubed]

How would I test this for myself ?
Is it going to be merged at some point by chance ?

[datacubed]

hey @sdispater it looks like this is merged into master ? I used the latest curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/master/install-poetry.py | python3.7 (from the release notes page, not the main site's documentation)
but im still getting the error where poetry cant find "python" though it should be using "python3" ?

[finswimmer]

Hey @datacubed,

the install-poetry.py script always installs the latest stable release. To install from master use https://raw.githubusercontent.com/python-poetry/poetry/master/install-poetry.py | python3.7 - --git https://github.com/python-poetry/poetry.git@master instead.

fin swimmer

[github-actions]

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