change BOOST_THROW to NDN_THROW

Change-Id: Ic5a0192302dd2965258d616fe163f3539b2104ea
diff --git a/src/identity-challenge/challenge-email.cpp b/src/identity-challenge/challenge-email.cpp
index 39dd162..f08025b 100644
--- a/src/identity-challenge/challenge-email.cpp
+++ b/src/identity-challenge/challenge-email.cpp
@@ -115,7 +115,7 @@
     result.push_back(std::make_tuple(PARAMETER_KEY_CODE, "Incorrect code, please try again"));
   }
   else {
-    BOOST_THROW_EXCEPTION(std::runtime_error("Unexpected status or challenge status."));
+    NDN_THROW(std::runtime_error("Unexpected status or challenge status."));
   }
   return result;
 }
@@ -126,7 +126,7 @@
   Block request = makeEmptyBlock(tlv_encrypted_payload);
   if (status == Status::BEFORE_CHALLENGE) {
     if (params.size() != 1 || std::get<0>(params[0]) != PARAMETER_KEY_EMAIL) {
-      BOOST_THROW_EXCEPTION(std::runtime_error("Wrong parameter provided."));
+      NDN_THROW(std::runtime_error("Wrong parameter provided."));
     }
     request.push_back(makeStringBlock(tlv_selected_challenge, CHALLENGE_TYPE));
     request.push_back(makeStringBlock(tlv_parameter_key, PARAMETER_KEY_EMAIL));
@@ -134,14 +134,14 @@
   }
   else if (status == Status::CHALLENGE && (challengeStatus == NEED_CODE || challengeStatus == WRONG_CODE)) {
     if (params.size() != 1 || std::get<0>(params[0]) != PARAMETER_KEY_CODE) {
-      BOOST_THROW_EXCEPTION(std::runtime_error("Wrong parameter provided."));
+      NDN_THROW(std::runtime_error("Wrong parameter provided."));
     }
     request.push_back(makeStringBlock(tlv_selected_challenge, CHALLENGE_TYPE));
     request.push_back(makeStringBlock(tlv_parameter_key, PARAMETER_KEY_CODE));
     request.push_back(makeStringBlock(tlv_parameter_value, std::get<1>(params[0])));
   }
   else {
-    BOOST_THROW_EXCEPTION(std::runtime_error("Unexpected status or challenge status."));
+    NDN_THROW(std::runtime_error("Unexpected status or challenge status."));
   }
   request.encode();
   return request;