avoid multiprocessing test usage in pypy

tests/build/common_include_dir.srctree

@@ -14,18 +14,21 @@ PYTHON fake_grep.py -c '#include "common/AddTraceback_impl_.*h"' c.c
 
 ######## setup.py ########
 
+import sys
 from Cython.Build.Dependencies import cythonize
 
 from distutils.core import setup
 
 # Test concurrent safety if multiprocessing is available.
 # (In particular, TravisCI does not support spawning processes from tests.)
-try:
-    import multiprocessing
-    multiprocessing.Pool(2).close()
-    nthreads = 2
-except (ImportError, OSError):
-    nthreads = 0
+nthreads = 0
+if not hasattr(sys, 'pypy_version_info'):
+    try:
+        import multiprocessing
+        multiprocessing.Pool(2).close()
+        nthreads = 2
+    except (ImportError, OSError):
+        pass
 
 setup(
   ext_modules = cythonize("*.pyx", common_utility_include_dir='common', nthreads=nthreads),