Issue 3807: multiprocessing fails to compile under --without-threads

Misc/NEWS

@@ -145,6 +145,10 @@ Core and Builtins
 Library
 -------
 
+- Issue #3807: _multiprocessing build fails when configure is passed 
+  --without-threads argument. When this occurs, _multiprocessing will
+  be disabled, and not compiled.
+
 - Issue #5008: When a file is opened in append mode with the new IO library,
   do an explicit seek to the end of file (so that e.g. tell() returns the
   file size rather than 0). This is consistent with the behaviour of the

setup.py

@@ -1315,9 +1315,13 @@ class PyBuildExt(build_ext):
             if macros.get('HAVE_SEM_OPEN', False):
                 multiprocessing_srcs.append('_multiprocessing/semaphore.c')
 
-        exts.append ( Extension('_multiprocessing', multiprocessing_srcs,
-                                 define_macros=macros.items(),
-                                 include_dirs=["Modules/_multiprocessing"]))
+        if sysconfig.get_config_var('WITH_THREAD'):
+            exts.append ( Extension('_multiprocessing', multiprocessing_srcs,
+                                    define_macros=macros.items(),
+                                    include_dirs=["Modules/_multiprocessing"]))
+        else:
+            missing.append('_multiprocessing')
+
         # End multiprocessing