make m2crypto backed public key pickleable

Author: tomato42

tlslite/utils/openssl_rsakey.py

@@ -43,6 +43,22 @@ def __init__(self, n=0, e=0, key_type="rsa"):
                 m2.rsa_set_e(self.rsa, numberToMPI(e))
             self.key_type = key_type
 
+        def __getstate__(self):
+            if not self.rsa:
+                return (self.key_type, )
+            return (self.key_type,
+                    mpiToNumber(m2.rsa_get_e(self.rsa)),
+                    mpiToNumber(m2.rsa_get_n(self.rsa)))
+
+        def __setstate__(self, state):
+            self.rsa = None
+            self._hasPrivateKey = False
+            self.key_type = state[0]
+            if len(state) > 1:
+                self.rsa = m2.rsa_new()
+                m2.rsa_set_e(self.rsa, numberToMPI(state[1]))
+                m2.rsa_set_n(self.rsa, numberToMPI(state[2]))
+
         def __del__(self):
             if self.rsa:
                 m2.rsa_free(self.rsa)