bpo-31904: Don't build the _crypt extension on VxWorks (GH-12833)

Doc/library/crypt.rst

@@ -30,6 +30,8 @@ the :manpage:`crypt(3)` routine in the running system.  Therefore, any
 extensions available on the current implementation will also  be available on
 this module.
 
+.. availability:: Unix. Not available on VxWorks.
+
 Hashing Methods
 ---------------
 

Misc/NEWS.d/next/Build/2019-04-15-15-01-29.bpo-31904.38fdkg.rst

+Don't build the ``_crypt`` extension on VxWorks.

setup.py

@@ -973,16 +973,17 @@ class PyBuildExt(build_ext):
 
     def detect_crypt(self):
         # crypt module.
+        if VXWORKS:
+            # bpo-31904: crypt() function is not provided by VxWorks.
+            # DES_crypt() OpenSSL provides is too weak to implement
+            # the encryption.
+            return
+
         if self.compiler.find_library_file(self.lib_dirs, 'crypt'):
             libs = ['crypt']
         else:
             libs = []
 
-        if not VXWORKS:
-            self.add(Extension('_crypt', ['_cryptmodule.c'],
-                               libraries=libs))
-        elif self.compiler.find_library_file(self.lib_dirs, 'OPENSSL'):
-            libs = ['OPENSSL']
         self.add(Extension('_crypt', ['_cryptmodule.c'],
                                libraries=libs))