Remove a Network::Exception that isn't one.

Code smell pointed out by Coverity.

src/network/network.cc

@@ -249,8 +249,7 @@ Connection::Connection( const char *desired_ip, const char *desired_port ) /* se
     RTT_hit( false ),
     SRTT( 1000 ),
     RTTVAR( 500 ),
-    have_send_exception( false ),
-    send_exception()
+    send_error()
 {
   setup();
 
@@ -369,8 +368,7 @@ Connection::Connection( const char *key_str, const char *ip, const char *port )
     RTT_hit( false ),
     SRTT( 1000 ),
     RTTVAR( 500 ),
-    have_send_exception( false ),
-    send_exception()
+    send_error()
 {
   setup();
 
@@ -405,14 +403,10 @@ void Connection::send( const string & s )
   ssize_t bytes_sent = sendto( sock(), p.data(), p.size(), MSG_DONTWAIT,
 			       &remote_addr.sa, remote_addr_len );
 
-  if ( bytes_sent == static_cast<ssize_t>( p.size() ) ) {
-    have_send_exception = false;
-  } else {
-    /* Notify the frontend on sendto() failure, but don't alter control flow.
-       sendto() success is not very meaningful because packets can be lost in
-       flight anyway. */
-    have_send_exception = true;
-    send_exception = NetworkException( "sendto", errno );
+  if ( bytes_sent != static_cast<ssize_t>( p.size() ) ) {
+    /* Make sendto() failure available to the frontend. */
+    send_error = "sendto: ";
+    send_error += strerror( errno );
 
     if ( errno == EMSGSIZE ) {
       MTU = DEFAULT_SEND_MTU; /* payload MTU of last resort */

src/network/network.h

@@ -187,10 +187,8 @@ namespace Network {
     double SRTT;
     double RTTVAR;
 
-    /* Exception from send(), to be delivered if the frontend asks for it,
-       without altering control flow. */
-    bool have_send_exception;
-    NetworkException send_exception;
+    /* Error from send()/sendto(). */
+    string send_error;
 
     Packet new_packet( const string &s_payload );
 
@@ -226,9 +224,9 @@ namespace Network {
     const Addr &get_remote_addr( void ) const { return remote_addr; }
     socklen_t get_remote_addr_len( void ) const { return remote_addr_len; }
 
-    const NetworkException *get_send_exception( void ) const
+    string &get_send_error( void )
     {
-      return have_send_exception ? &send_exception : NULL;
+      return send_error;
     }
 
     void set_last_roundtrip_success( uint64_t s_success ) { last_roundtrip_success = s_success; }

src/network/networktransport.h

@@ -119,7 +119,7 @@ namespace Network {
     const Addr &get_remote_addr( void ) const { return connection.get_remote_addr(); }
     socklen_t get_remote_addr_len( void ) const { return connection.get_remote_addr_len(); }
 
-    const NetworkException *get_send_exception( void ) const { return connection.get_send_exception(); }
+    std::string &get_send_error( void ) { return connection.get_send_error(); }
   };
 }