Extension shows install pytest prompt when test discovery fails due to missing some another module

[karthiknadig]

Environment data

• VS Code version: 1.34.0
• Extension version (available under the Extensions sidebar): 2019.6.16302-dev
• OS and version: windows
• Python version (& distribution if applicable, e.g. Anaconda): 3.7
• Type of virtual environment used (N/A | venv | virtualenv | conda | ...): N/A
• Relevant/affected Python packages and their versions: pytest

Expected behaviour

Should not show pytest install prompt, if pytest is installed. Insted say test discovery failed.
Bonus points if it can identify which module is actually missing ans show the right prompt.

Actual behaviour

Steps to reproduce:

1. Use these settings:

{
    "python.pythonPath": "C:\\Python37\\python.exe",
    "python.testing.pyTestEnabled": true,
    "python.testing.nosetestsEnabled": false,
    "python.testing.unittestEnabled": false,
    "python.testing.pyTestArgs": [
        "."
    ],
}

2. Add a file in root dir that imports some module that is not installed.
   pyqt_test.py:

from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *

# this is enough to get the prompt.

Logs

______________________ ERROR collecting pyqtapp_test.py _______________________
ImportError while importing test module 'c:\GIT\pyscratch2\pyqtapp_test.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
pyqtapp_test.py:1: in <module>
    from PyQt5.QtGui import *
E   ModuleNotFoundError: No module named 'PyQt5'
!!!!!!!!!!!!!!!!!!! Interrupted: 1 errors during collection !!!!!!!!!!!!!!!!!!!
=========================== 1 error in 0.10 seconds ===========================

Traceback (most recent call last):
  File "C:\Users\kanadig\.vscode\extensions\ms-python.python-2019.6.16302-dev\pythonFiles\testing_tools\run_adapter.py", line 16, in <module>
    main(tool, cmd, subargs, toolargs)
  File "C:\Users\kanadig\.vscode\extensions\ms-python.python-2019.6.16302-dev\pythonFiles\testing_tools\adapter\__main__.py", line 90, in main
    parents, result = run(toolargs, **subargs)
  File "C:\Users\kanadig\.vscode\extensions\ms-python.python-2019.6.16302-dev\pythonFiles\testing_tools\adapter\pytest\_discovery.py", line 35, in discover
    raise Exception('pytest discovery failed (exit code {})'.format(ec))
Exception: pytest discovery failed (exit code 2)

[erihanse]

I have the same problem, except that it only fails for my own modules. If I install version 2019.3.6558 of the extension it works, and tests are discovered.

EDIT:
The latest version I got it to work with was 2019.5.x.
After reading this thread: #6347 (comment) I realised normal behaviour would be resolved by adding an .env file containing PYTHONPATH=..

[warnes]

I can confirm this error for myself and several colleagues.

[karrtikr]

Fixed with latest extension.