Disable index URL in pip-based fetch_build_eggs to avoid hitting PyPI.

setuptools/tests/test_virtualenv.py

@@ -181,6 +181,8 @@ def test_test_command_install_requirements(virtualenv, tmpdir):
         "python -c \"__import__('pkg_resources').require(['pip', 'wheel'])\"")
     # uninstall setuptools so that 'setup.py develop' works
     virtualenv.run("python -m pip uninstall -y setuptools")
+    # disable index URL so bits and bobs aren't requested from PyPI
+    virtualenv.env['PIP_NO_INDEX'] = '1'
     _check_test_command_install_requirements(virtualenv, tmpdir)