test: move HasReason so it can be reused

Move the class `HasReason` from `miner_tests.cpp` to
`setup_common.h` so that it can be reused by other tests.

src/test/miner_tests.cpp

@@ -36,17 +36,6 @@ struct MinerTestingSetup : public TestingSetup {
 
 BOOST_FIXTURE_TEST_SUITE(miner_tests, MinerTestingSetup)
 
-// BOOST_CHECK_EXCEPTION predicates to check the specific validation error
-class HasReason {
-public:
-    explicit HasReason(const std::string& reason) : m_reason(reason) {}
-    bool operator() (const std::runtime_error& e) const {
-        return std::string(e.what()).find(m_reason) != std::string::npos;
-    };
-private:
-    const std::string m_reason;
-};
-
 static CFeeRate blockMinFeeRate = CFeeRate(DEFAULT_BLOCK_MIN_TX_FEE);
 
 BlockAssembler MinerTestingSetup::AssemblerForTest(const CChainParams& params)

src/test/util/setup_common.h

@@ -153,4 +153,20 @@ CBlock getBlock13b8a();
 // define an implicit conversion here so that uint256 may be used directly in BOOST_CHECK_*
 std::ostream& operator<<(std::ostream& os, const uint256& num);
 
+/**
+ * BOOST_CHECK_EXCEPTION predicates to check the specific validation error.
+ * Use as
+ * BOOST_CHECK_EXCEPTION(code that throws, exception type, HasReason("foo"));
+ */
+class HasReason {
+public:
+    explicit HasReason(const std::string& reason) : m_reason(reason) {}
+    template <typename E>
+    bool operator() (const E& e) const {
+        return std::string(e.what()).find(m_reason) != std::string::npos;
+    };
+private:
+    const std::string m_reason;
+};
+
 #endif