[3.15] gh-151096: Fix test_embed with split exec prefix (GH-151288) (#152590)

gh-151096: Fix test_embed with split exec prefix (GH-151288)
(cherry picked from commit b19839b)

Co-authored-by: Harjoth Khara <harjoth.khara@gmail.com>

Author: miss-islington

Lib/test/test_embed.py

@@ -1429,7 +1429,7 @@ def module_search_paths(self, prefix=None, exec_prefix=None):
         if prefix is None:
             prefix = config['config']['prefix']
         if exec_prefix is None:
-            exec_prefix = config['config']['prefix']
+            exec_prefix = config['config']['exec_prefix']
         if MS_WINDOWS:
             return config['config']['module_search_paths']
         else:
@@ -1578,8 +1578,10 @@ def test_init_is_python_build_with_home(self):
             expected_paths[1 if MS_WINDOWS else 2] = os.path.normpath(
                 os.path.join(exedir, f'{f.read()}\n$'.splitlines()[0]))
         if not MS_WINDOWS:
-            # PREFIX (default) is set when running in build directory
-            prefix = exec_prefix = sys.prefix
+            # PREFIX and EXEC_PREFIX (defaults) are set when running in the
+            # build directory and may differ with --exec-prefix (gh-151096).
+            prefix = sys.prefix
+            exec_prefix = sys.exec_prefix
             # stdlib calculation (/Lib) is not yet supported
             expected_paths[0] = self.module_search_paths(prefix=prefix)[0]
             config.update(prefix=prefix, base_prefix=prefix,

Misc/NEWS.d/next/Tests/2026-06-16-05-11-38.gh-issue-151096.Kq3Lp9.rst

@@ -0,0 +1,2 @@
+Fix ``test_embed`` failing when CPython is configured with a split exec prefix
+(``--exec-prefix`` differing from ``--prefix``).