feat: support Windows workaround on Travis CI

Author: henryiii

cibuildwheel/windows.py

@@ -70,7 +70,8 @@ def get_python_configurations(
         '64': Architecture.AMD64,
     }
 
-    if IS_RUNNING_ON_TRAVIS:
+    custom_compiler = os.environ.get('DISTUTILS_USE_SDK') and os.environ.get('MSSdk')
+    if IS_RUNNING_ON_TRAVIS and not custom_compiler:
         # cannot install VCForPython27.msi which is needed for compiling C software
         # try with (and similar): msiexec /i VCForPython27.msi ALLUSERS=1 ACCEPT=YES /passive
         python_configurations = [c for c in python_configurations if not c.version.startswith('2.7')]

docs/setup.md

@@ -44,7 +44,7 @@ To build Linux, Mac, and Windows wheels on Travis CI, create a `.travis.yml` fil
 {% include "../examples/travis-ci-minimal.yml" %}
 ```
 
-Note that building Windows Python 2.7 wheels on Travis is unsupported.
+Note that building Windows Python 2.7 wheels on Travis is unsupported unless using a newer compiler [via a workaround](cpp-standards.md).
 
 Commit this file, enable building of your repo on Travis CI, and push.
 

test/utils.py

@@ -134,7 +134,8 @@ def expected_wheels(package_name, package_version, manylinux_versions=None,
         for platform_tag in platform_tags:
             wheels.append(f'{package_name}-{package_version}-{python_abi_tag}-{platform_tag}.whl')
 
-    if IS_WINDOWS_RUNNING_ON_TRAVIS:
+    custom_compiler = os.environ.get('DISTUTILS_USE_SDK') and os.environ.get('MSSdk')
+    if IS_WINDOWS_RUNNING_ON_TRAVIS and not custom_compiler:
         # Python 2.7 isn't supported on Travis.
         wheels = [w for w in wheels if '-cp27-' not in w and '-pp2' not in w]