refactor(library/tactic): remove unnecessary tactic_exception

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/library/tactic/proof_state.cpp

@@ -5,7 +5,6 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Author: Leonardo de Moura
 */
 #include "util/sstream.h"
-#include "library/tactic/tactic_exception.h"
 #include "library/tactic/proof_state.h"
 
 namespace lean {

src/library/tactic/tactic.cpp

@@ -10,7 +10,6 @@ Author: Leonardo de Moura
 #include "util/sstream.h"
 #include "util/interrupt.h"
 #include "util/lazy_list_fn.h"
-#include "library/tactic/tactic_exception.h"
 #include "library/tactic/tactic.h"
 
 namespace lean {

src/library/tactic/tactic_exception.h

@@ -1,25 +0,0 @@
-/*
-Copyright (c) 2013 Microsoft Corporation. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-
-Author: Leonardo de Moura
-*/
-#pragma once
-#include <string>
-#include "util/exception.h"
-#include "kernel/justification.h"
-
-namespace lean {
-/**
-   \brief Tactic and related components store the reason for
-   failure in justification objects.
-*/
-class tactic_exception : public exception {
-    justification m_justification;
-public:
-    tactic_exception(justification const & j):m_justification(j) {}
-    virtual ~tactic_exception() {}
-    virtual char const * what() const noexcept { return "tactic exception"; }
-    justification const & get_justification() const { return m_justification; }
-};
-}