Add comments/docstrings not to use md5 unless forced to by forces outside our control.

lib/ansible/module_utils/basic.py

@@ -1238,7 +1238,16 @@ class AnsibleModule(object):
         return digest.hexdigest()
 
     def md5(self, filename):
-        ''' Return MD5 hex digest of local file using digest_from_file(). '''
+        ''' Return MD5 hex digest of local file using digest_from_file().
+
+        Do not use this function unless you have no other choice for:
+            1) Optional backwards compatibility
+            2) Compatibility with a third party protocol
+
+        This function will not work on systems complying with FIPS-140-2.
+
+        Most uses of this function can use the module.sha1 function instead.
+        '''
         return self.digest_from_file(filename, _md5())
 
     def sha1(self, filename):

lib/ansible/utils/__init__.py

@@ -864,6 +864,11 @@ checksum_s = secure_hash_s
 # Backwards compat.  Some modules include md5s in their return values
 # Continue to support that for now.  As of ansible-1.8, all of those modules
 # should also return "checksum" (sha1 for now)
+# Do not use m5 unless it is needed for:
+# 1) Optional backwards compatibility
+# 2) Compliance with a third party protocol
+#
+# MD5 will not work on systems which are FIPS-140-2 compliant.
 def md5s(data):
     return secure_hash_s(data, _md5)