change 02_test to check if virtualenv is properly used

cibuildwheel/linux.py

@@ -145,6 +145,8 @@ def build(project_dir, output_dir, test_command, test_requires, test_extras, bef
                     venv_dir=`mktemp -d`/venv
                     python -m virtualenv "$venv_dir"
 
+                    export __CIBW_VIRTUALENV_PATH__=$venv_dir
+
                     # run the tests in a subshell to keep that `activate`
                     # script from polluting the env
                     (

cibuildwheel/macos.py

@@ -209,6 +209,7 @@ def build(project_dir, output_dir, test_command, test_requires, test_extras, bef
                 os.path.join(venv_dir, 'bin'),
                 virtualenv_env['PATH'],
             ])
+            virtualenv_env["__CIBW_VIRTUALENV_PATH__"] = venv_dir
 
             # check that we are using the Python from the virtual environment
             call(['which', 'python'], env=virtualenv_env)

cibuildwheel/windows.py

@@ -197,6 +197,7 @@ def build(project_dir, output_dir, test_command, test_requires, test_extras, bef
                 os.path.join(venv_dir, 'Scripts'),
                 virtualenv_env['PATH'],
             ])
+            virtualenv_env["__CIBW_VIRTUALENV_PATH__"] = venv_dir
 
             # check that we are using the Python from the virtual environment
             shell(['which', 'python'], env=virtualenv_env)