diff --git a/cibuildwheel/__main__.py b/cibuildwheel/__main__.py
index bdc76287..6252b4f2 100644
--- a/cibuildwheel/__main__.py
+++ b/cibuildwheel/__main__.py
@@ -177,11 +177,10 @@ def detect_warnings(platform, build_options):
 
     # warn about deprecated {python} and {pip}
     for option_name in ['test_command', 'before_build']:
-        option_value = build_options.get(option_name)
+        option_value = build_options.get(option_name, '')
 
-        if option_value:
-            if '{python}' in option_value or '{pip}' in option_value:
-                warnings.append(option_name + ": '{python}' and '{pip}' are no longer needed, and will be removed in a future release. Simply use 'python' or 'pip' instead.")
+        if '{python}' in option_value or '{pip}' in option_value:
+            warnings.append(option_name + ": '{python}' and '{pip}' are no longer needed, and will be removed in a future release. Simply use 'python' or 'pip' instead.")
 
     return warnings
 
diff --git a/cibuildwheel/macos.py b/cibuildwheel/macos.py
index 569f14a9..45cb178a 100644
--- a/cibuildwheel/macos.py
+++ b/cibuildwheel/macos.py
@@ -47,13 +47,14 @@ def build(project_dir, package_name, output_dir, test_command, test_requires, be
 
         # if this version of python isn't installed, get it from python.org and install
         python_package_identifier = 'org.python.Python.PythonFramework-%s' % config.version
-        installation_bin_path = '/Library/Frameworks/Python.framework/Versions/{}/bin'.format(config.version)
         if python_package_identifier not in installed_system_packages:
             # download the pkg
             call(['curl', '-L', '-o', '/tmp/Python.pkg', config.url])
             # install
             call(['sudo', 'installer', '-pkg', '/tmp/Python.pkg', '-target', '/'])
 
+        installation_bin_path = '/Library/Frameworks/Python.framework/Versions/{}/bin'.format(config.version)
+
         # Python bin folders on Mac don't symlink python3 to python, so we do that
         # so `python` and `pip` always point to the active configuration.
         if os.path.exists('/tmp/cibw_bin'):