Use the same mechanism on mac for ensuring default-pip

cibuildwheel/macos.py

@@ -232,11 +232,22 @@ def setup_python(
         sys.exit(1)
 
     # ensure pip is installed
-    call(
+    if not (installation_bin_path / "pip").exists():
-        ["python", "-m", "ensurepip", "--default-pip"],
+        # perhaps pip is installed, but not available as 'pip'...
-        env=env,
+        try:
-        cwd="/tmp",
+            call(["python", "-m", "pip", "--version"], env=env, cwd="/tmp")
-    )
+        except subprocess.CalledProcessError:
+            pip_is_installed = False
+        else:
+            pip_is_installed = True
+
+        if pip_is_installed:
+            # if it's there, remove that version of pip.
+            call(["python", "-m", "pip", "uninstall", "--yes", "pip"], env=env, cwd="C:\\cibw")
+
+        # Then reinstall. '--default-pip' ensures that it's installed as 'pip'
+        call(["python", "-m", "ensurepip", "--default-pip"], env=env, cwd="C:\\cibw")
+
     # ensure we have the version that matches our constraints
     call(
         ["python", "-m", "pip", "install", "--upgrade", "pip", *dependency_constraint_flags],