Catch traceback caused by permissions errors during a local md5 sum

Fixes #6948

lib/ansible/utils/__init__.py

@@ -590,12 +590,15 @@ def md5(filename):
         return None
     digest = _md5()
     blocksize = 64 * 1024
+    try:
         infile = open(filename, 'rb')
         block = infile.read(blocksize)
         while block:
             digest.update(block)
             block = infile.read(blocksize)
         infile.close()
+    except IOError, e:
+        raise errors.AnsibleError("error while accessing the file %s, error was: %s" % (filename, e))
     return digest.hexdigest()
 
 def default(value, function):