Fix CacheDir initialization so works on 3.7 also

CHANGES.txt

@@ -18,6 +18,8 @@ RELEASE  VERSION/DATE TO BE FILLED IN LATER
   From Mats Wichmann:
     - Fix typos in CCFLAGS test. Didn't affect the test itself, but
       didn't correctly apply the DefaultEnvironment speedup.
+    - New CacheDir initialization code failed on Python 3.7 for unknown
+      reason (worked on 3.8+). Adjusted the approach a bit.  Fixes #4694.
 
 
 RELEASE 4.9.0 -  Sun, 02 Mar 2025 17:22:20 -0700

RELEASE.txt

@@ -34,6 +34,9 @@ FIXES
 
 - List fixes of outright bugs
 
+- New CacheDir initialization code failed on Python 3.7 for unknown
+  reason (worked on 3.8+). Adjusted the approach a bit.  Fixes #4694.
+
 IMPROVEMENTS
 ------------
 

SCons/CacheDir.py

@@ -27,6 +27,7 @@
 import atexit
 import json
 import os
+import shutil
 import stat
 import sys
 import tempfile
@@ -76,7 +77,6 @@ def CacheRetrieveFunc(target, source, env) -> int:
 
 def CacheRetrieveString(target, source, env) -> str:
     t = target[0]
-    fs = t.fs
     cd = env.get_CacheDir()
     cachedir, cachefile = cd.cachepath(t)
     if t.fs.exists(cachefile):
@@ -209,22 +209,28 @@ def _mkdir_atomic(self, path: str) -> bool:
         if os.path.exists(directory):
             return False
 
+        # TODO: tried to use TemporaryDirectory() here and the result as a
+        #   context manager, but that fails on Python 3.7 (works on 3.8+) after
+        #   the directory has successfully been renamed. Not sure why.
         try:
-            tempdir = tempfile.TemporaryDirectory(dir=os.path.dirname(directory))
+            tempdir = tempfile.mkdtemp(dir=os.path.dirname(directory))
         except OSError as e:
             msg = "Failed to create cache directory " + path
             raise SCons.Errors.SConsEnvironmentError(msg) from e
-        self._add_config(tempdir.name)
-        with tempdir:
-            try:
-                os.rename(tempdir.name, directory)
-                return True
-            except Exception as e:
-                # did someone else get there first?
-                if os.path.isdir(directory):
-                    return False
-                msg = "Failed to create cache directory " + path
-                raise SCons.Errors.SConsEnvironmentError(msg) from e
+        self._add_config(tempdir)
+        try:
+            os.replace(tempdir, directory)
+            return True
+        except OSError as e:
+            # did someone else get there first? attempt cleanup.
+            if os.path.isdir(directory):
+                try:
+                    shutil.rmtree(tempdir)
+                except Exception:  # we tried, don't worry about it
+                    pass
+                return False
+            msg = "Failed to create cache directory " + path
+            raise SCons.Errors.SConsEnvironmentError(msg) from e
 
     def _readconfig(self, path: str) -> None:
         """Read the cache config from *path*.