Rework custom test machinery to give the individual tests more control

on how they're run, and combine environment.json and check.py

test/05_environment/cibuildwheel_test.py

@@ -0,0 +1,22 @@
+import subprocess, sys, os
+from glob import glob
+project_dir = os.path.dirname(__file__)
+sys.path.append(os.path.join(os.path.dirname(project_dir), 'shared'))
+import utils
+
+def test():
+    # set up the environment
+    env = os.environ.copy()
+    # write some information into the CIBW_ENVIRONMENT, for expansion and
+    # insertion into the environment by cibuildwheel. This is checked
+    # in setup.py
+    env['CIBW_ENVIRONMENT'] = 'CIBW_TEST_VAR="a b c" CIBW_TEST_VAR_2=1 CIBW_TEST_VAR_3="$(echo \'test string 3\')" PATH=$PATH:/opt/cibw_test_path',
+    env['CIBW_ENVIRONMENT_WINDOWS'] = 'CIBW_TEST_VAR="a b c" CIBW_TEST_VAR_2=1 CIBW_TEST_VAR_3="$(echo \'test string 3\')" PATH="$PATH;/opt/cibw_test_path"'
+
+    # build the wheels
+    subprocess.check_call([sys.executable, '-m', 'cibuildwheel', project_dir], env=env)
+    
+    # check that we got the right number of built wheels
+    expected_identifiers = utils.cibuildwheel_get_build_identifiers(project_dir)
+    built_wheels = glob('wheelhouse/*.whl')
+    assert len(built_wheels) == len(expected_identifiers)