use python instead of python3 everywhere

Everywhere: on CI, in tests, in docs. Also, we replace bare pip/pip3 and pytest calls with python -m pip and python -m pytest respectively, to make sure we always use the same python executable everywhere.

This fixes #326 (failing Windows tests on CI), because the `python3` executable causes issues (it is not properly copied into the venv directory by venv, which is a CPython bug, see python/cpython#87915), while the python executable does work; see e.g. here https://stackoverflow.com/questions/61669873/python-venv-env-fails-winerror-2-the-system-cannot-find-the-file-specified. `python` should be the same executable under the hood as `python3`, if the setup-python action works as expected, at least.
It also allows us to remove the IS_WINDOWS_CI special case.

Failed attempts at fixing #326 included:
- Setting the shells (assuming something went wrong with environment
  variables)
- Using full paths for both the executable and the venv directory in the
  template test suite.

.github/workflows/tests.yml

@@ -26,12 +26,12 @@ jobs:
     - name: Python info
       shell: bash -l {0}
       run: |
-        which python3
-        python3 --version
+        which python
+        python --version
     - name: Install dependencies
       run: |
-        python3 -m pip install --upgrade pip setuptools
-        python3 -m pip install .[dev]
+        python -m pip install --upgrade pip setuptools
+        python -m pip install .[dev]
     - name: Run pytest
       run: |
-        pytest -v
+        python -m pytest -v

README.dev.md

@@ -10,7 +10,7 @@ We recommend installing `cookiecutter` in user space as per `cookiecutter`'s ins
 install `cookiecutter` for every new project.
 
 ```shell
-python3 -m pip install --user --upgrade cookiecutter
+python -m pip install --user --upgrade cookiecutter
 ```
 
 ### Get your own copy of the repository
@@ -30,17 +30,17 @@ run the tests later.
 
 ```shell
 # Create a virtual environment, e.g. with
-python3 -m venv env
+python -m venv env
 
 # activate virtual environment
 source env/bin/activate
 
 # make sure to have a recent version of pip and setuptools
-python3 -m pip install --upgrade pip setuptools
+python -m pip install --upgrade pip setuptools
 
 # (from the project root directory)
 # install development dependencies
-python3 -m pip install --no-cache-dir .[dev]
+python -m pip install --no-cache-dir .[dev]
 ```
 
 ## Running the tests

tests/test_project.py

@@ -1,14 +1,11 @@
 import os
 import subprocess
-from pathlib import Path
-from shutil import which
 from sys import platform
 from typing import Sequence
 
 import pytest
 
 IS_WINDOWS = platform.startswith('win')
-IS_WINDOWS_CI = IS_WINDOWS and os.environ.get('CI', False)
 
 
 def test_project_folder(cookies):
@@ -33,17 +30,11 @@ def run(args: Sequence[str], dirpath: os.PathLike) -> subprocess.CompletedProces
 
 @pytest.fixture
 def project_env_bin_dir(tmp_path):
-    if IS_WINDOWS_CI:
-        # Creating virtualenv does not work on Windows CI,
-        # falling back to using current pip3 dir
-        pip = Path(which('pip3'))
-        bin_dir = pip.parent
-    else:
-        env_output = run(['python3', '-m', 'venv', 'env'], tmp_path)
-        assert env_output.returncode == 0
-        bin_dir = str(tmp_path / 'env' / 'bin')
-        if IS_WINDOWS:
-            bin_dir = str(tmp_path / 'env' / 'Scripts')
+    env_output = run(['python', '-m', 'venv', 'env'], tmp_path)
+    assert env_output.returncode == 0
+    bin_dir = str(tmp_path / 'env' / 'bin')
+    if IS_WINDOWS:
+        bin_dir = str(tmp_path / 'env' / 'Scripts')
     return str(bin_dir) + os.sep
 
 
@@ -52,17 +43,17 @@ def baked_with_development_dependencies(cookies, project_env_bin_dir):
     result = cookies.bake()
     assert result.exit_code == 0
     bin_dir = project_env_bin_dir
-    latest_pip_output = run([f'{bin_dir}pip3', 'install', '--upgrade', 'pip', 'setuptools'], result.project)
+    latest_pip_output = run([f'{bin_dir}python', '-m', 'pip', 'install', '--upgrade', 'pip', 'setuptools'], result.project)
     assert latest_pip_output.returncode == 0
-    pip_output = run([f'{bin_dir}pip3', 'install', '--editable', '.[dev]'], result.project)
+    pip_output = run([f'{bin_dir}python', '-m', 'pip', 'install', '--editable', '.[dev]'], result.project)
     assert pip_output.returncode == 0
     return result.project
 
 
 def test_pytest(baked_with_development_dependencies, project_env_bin_dir):
     project_dir = baked_with_development_dependencies
     bin_dir = project_env_bin_dir
-    result = run([f'{bin_dir}pytest'], project_dir)
+    result = run([f'{bin_dir}python', '-m', 'pytest'], project_dir)
     assert result.returncode == 0
     assert '== 3 passed in' in result.stdout
 
@@ -98,9 +89,6 @@ def test_subpackage(baked_with_development_dependencies, project_env_bin_dir):
     subsubpackage.mkdir()
     (subsubpackage / '__init__.py').write_text('FOO = "bar"', encoding="utf-8")
 
-    if IS_WINDOWS_CI:
-        # On Windows CI python and pip executable are in different paths
-        bin_dir = ''
     # sdist and bdist_wheel both call build command to create build/ dir
     # So instead of looking in distribution archives we can look in build/ dir
     result = run([f'{bin_dir}python', 'setup.py', 'build'], project_dir)

{{cookiecutter.directory_name}}/.github/workflows/build.yml

@@ -27,16 +27,16 @@ jobs:
       - name: Python info
         shell: bash -l {0}
         run: |
-          which python3
-          python3 --version
+          which python
+          python --version
       - name: Upgrade pip and install dependencies
         run: |
-          python3 -m pip install --upgrade pip setuptools
-          python3 -m pip install .[dev,publishing]
+          python -m pip install --upgrade pip setuptools
+          python -m pip install .[dev,publishing]
       - name: Run unit tests
-        run: pytest -v
+        run: python -m pytest -v
       - name: Verify that we can build the package
-        run: python3 setup.py sdist bdist_wheel
+        run: python setup.py sdist bdist_wheel
 
   lint:
     name: Linting build
@@ -52,12 +52,12 @@ jobs:
       - name: Python info
         shell: bash -l {0}
         run: |
-          which python3
-          python3 --version
+          which python
+          python --version
       - name: Upgrade pip and install dependencies
         run: |
-          python3 -m pip install --upgrade pip setuptools
-          python3 -m pip install .[dev,publishing]
+          python -m pip install --upgrade pip setuptools
+          python -m pip install .[dev,publishing]
       - name: Check style against standards using prospector
         run: prospector
       - name: Check import order

{{cookiecutter.directory_name}}/.github/workflows/documentation.yml

@@ -23,12 +23,12 @@ jobs:
       - name: Python info
         shell: bash -l {0}
         run: |
-          which python3
-          python3 --version
+          which python
+          python --version
       - name: Upgrade pip and install dependencies
         run: |
-          python3 -m pip install --upgrade pip setuptools
-          python3 -m pip install .[dev,publishing]
+          python -m pip install --upgrade pip setuptools
+          python -m pip install .[dev,publishing]
       - name: Install pandoc using apt
         run: sudo apt install pandoc        
       - name: Build documentation

{{cookiecutter.directory_name}}/.github/workflows/sonarcloud.yml

@@ -25,14 +25,14 @@ jobs:
       - name: Python info
         shell: bash -l {0}
         run: |
-          which python3
-          python3 --version
+          which python
+          python --version
       - name: Install dependencies
-        run: python3 -m pip install .[dev]
+        run: python -m pip install .[dev]
       - name: Check style against standards using prospector
         run: prospector --zero-exit --output-format grouped --output-format pylint:pylint-report.txt
       - name: Run unit tests with coverage
-        run: pytest --cov --cov-report term --cov-report xml --junitxml=xunit-result.xml tests/
+        run: python -m pytest --cov --cov-report term --cov-report xml --junitxml=xunit-result.xml tests/
       - name: Correct coverage paths
         run: sed -i "s+$PWD/++g" coverage.xml
       - name: SonarCloud Scan

{{cookiecutter.directory_name}}/README.dev.md

@@ -6,19 +6,19 @@ If you're looking for user documentation, go [here](README.md).
 
 ```shell
 # Create a virtual environment, e.g. with
-python3 -m venv env
+python -m venv env
 
 # activate virtual environment
 source env/bin/activate
 
 # make sure to have a recent version of pip and setuptools
-python3 -m pip install --upgrade pip setuptools
+python -m pip install --upgrade pip setuptools
 
 # (from the project root directory)
 # install {{ cookiecutter.package_name }} as an editable package
-python3 -m pip install --no-cache-dir --editable .
+python -m pip install --no-cache-dir --editable .
 # install development dependencies
-python3 -m pip install --no-cache-dir --editable .[dev]
+python -m pip install --no-cache-dir --editable .[dev]
 ```
 
 Afterwards check that the install directory is present in the `PATH` environment variable.
@@ -156,22 +156,22 @@ cd $(mktemp -d {{ cookiecutter.package_name }}.XXXXXX)
 git clone {{ cookiecutter.repository }} .
 
 # prepare a clean virtual environment and activate it
-python3 -m venv env
+python -m venv env
 source env/bin/activate
 
 # make sure to have a recent version of pip and setuptools
-python3 -m pip install --upgrade pip setuptools
+python -m pip install --upgrade pip setuptools
 
 # install runtime dependencies and publishing dependencies
-python3 -m pip install --no-cache-dir .
-python3 -m pip install --no-cache-dir .[publishing]
+python -m pip install --no-cache-dir .
+python -m pip install --no-cache-dir .[publishing]
 
 # clean up any previously generated artefacts
 rm -rf {{ cookiecutter.package_name }}.egg-info
 rm -rf dist
 
 # create the source distribution and the wheel
-python3 setup.py sdist bdist_wheel
+python setup.py sdist bdist_wheel
 
 # upload to test pypi instance (requires credentials)
 twine upload --repository-url https://test.pypi.org/legacy/ dist/*
@@ -187,14 +187,14 @@ In a new terminal, without an activated virtual environment or an env directory:
 cd $(mktemp -d {{ cookiecutter.package_name }}-test.XXXXXX)
 
 # prepare a clean virtual environment and activate it
-python3 -m venv env
+python -m venv env
 source env/bin/activate
 
 # make sure to have a recent version of pip and setuptools
-pip install --upgrade pip setuptools
+python -m pip install --upgrade pip setuptools
 
 # install from test pypi instance:
-python3 -m pip -v install --no-cache-dir \
+python -m pip -v install --no-cache-dir \
 --index-url https://test.pypi.org/simple/ \
 --extra-index-url https://pypi.org/simple {{ cookiecutter.package_name }}
 ```