Add the --no-download flag to virtualenv, to prevent it getting the latest

version of pip, setuptools, wheel from PyPI on creation.

Virtualenv will use bundled version of those tools instead

cibuildwheel/linux.py

@@ -121,7 +121,7 @@ def build(project_dir, output_dir, test_command, test_requires, test_extras, bef
                             # there are no dependencies that were pulled in at build time.
                             pip install {dependency_install_flags} virtualenv
                             venv_dir=`mktemp -d`/venv
-                            python -m virtualenv "$venv_dir"
+                            python -m virtualenv --no-download "$venv_dir"
 
                             # run the tests in a subshell to keep that `activate`
                             # script from polluting the env

cibuildwheel/macos.py

@@ -140,7 +140,7 @@ def build(project_dir, output_dir, test_command, test_requires, test_extras, bef
             # there are no dependencies that were pulled in at build time.
             call(['pip', 'install', 'virtualenv'] + dependency_constraint_flags, env=env)
             venv_dir = tempfile.mkdtemp()
-            call(['python', '-m', 'virtualenv', venv_dir], env=env)
+            call(['python', '-m', 'virtualenv', '--no-download', venv_dir], env=env)
 
             virtualenv_env = env.copy()
             virtualenv_env['PATH'] = os.pathsep.join([

cibuildwheel/windows.py

@@ -152,7 +152,7 @@ def build(project_dir, output_dir, test_command, test_requires, test_extras, bef
             # there are no dependencies that were pulled in at build time.
             shell(['pip', 'install', 'virtualenv'] + dependency_constraint_flags, env=env)
             venv_dir = tempfile.mkdtemp()
-            shell(['python', '-m', 'virtualenv', venv_dir], env=env)
+            shell(['python', '-m', 'virtualenv', '--no-download', venv_dir], env=env)
 
             virtualenv_env = env.copy()
             virtualenv_env['PATH'] = os.pathsep.join([