tests: rework clean install test

Use pytest-virtualenv so the test can be run no Windows too.

.travis.yml

@@ -43,7 +43,4 @@ install:
 # update egg_info based on setup.py in checkout
 - python bootstrap.py
 
-# Check that setuptools can be installed in a clean environment
-- tests/clean_install.sh
-
 script: tox

setuptools/tests/test_virtualenv.py

+import os
+
+from pytest import yield_fixture
+from pytest_fixture_config import yield_requires_config
+
+import pytest_virtualenv
+
+
+@yield_requires_config(pytest_virtualenv.CONFIG, ['virtualenv_executable'])
+@yield_fixture(scope='function')
+def bare_virtualenv():
+    """ Bare virtualenv (no pip/setuptools/wheel).
+    """
+    with pytest_virtualenv.VirtualEnv(args=(
+        '--no-wheel',
+        '--no-pip',
+        '--no-setuptools',
+    )) as venv:
+        yield venv
+
+
+SOURCE_DIR = os.path.join(os.path.dirname(__file__), '../..')
+
+def test_clean_env_install(bare_virtualenv):
+    """
+    Check setuptools can be installed in a clean environment.
+    """
+    bare_virtualenv.run(' && '.join((
+        'cd {source}',
+        'python setup.py install',
+    )).format(source=SOURCE_DIR))

tests/clean_install.sh

-#!/usr/bin/env bash
-
-# This test was created in
-# https://github.com/pypa/setuptools/pull/1050
-# but it really should be incorporated into the test suite
-# such that it runs on Windows and doesn't depend on
-# virtualenv. Moving to test_integration will likely address
-# those concerns.
-
-set -o errexit
-set -o xtrace
-
-# Create a temporary directory to install the virtualenv in
-VENV_DIR="$(mktemp -d)"
-function cleanup() {
-  rm -rf "$VENV_DIR"
-}
-trap cleanup EXIT
-
-# Create a virtualenv that doesn't have pip or setuptools installed
-wget https://raw.githubusercontent.com/pypa/virtualenv/master/virtualenv.py
-python virtualenv.py --no-wheel --no-pip --no-setuptools "$VENV_DIR"
-source "$VENV_DIR/bin/activate"
-
-# Now try to install setuptools
-python bootstrap.py
-python setup.py install

tests/requirements.txt

+importlib; python_version<"2.7"
 mock
 pytest-flake8
+pytest-virtualenv>=1.2.7
 pytest>=3.0.2
+virtualenv