Revert "Re-add..."

This reverts commit b1faebae4a.

ext/libpqxx-7.7.3/test/unit/test_exceptions.cxx

@@ -1,45 +0,0 @@
-#include <pqxx/except>
-#include <pqxx/transaction>
-
-#include "../test_helpers.hxx"
-
-
-namespace
-{
-void test_exceptions()
-{
-  std::string const broken_query{"SELECT HORRIBLE ERROR"},
-    err{"Error message"};
-
-  try
-  {
-    throw pqxx::sql_error{err, broken_query};
-  }
-  catch (std::exception const &e)
-  {
-    PQXX_CHECK_EQUAL(e.what(), err, "Exception contains wrong message.");
-    auto downcast{dynamic_cast<pqxx::sql_error const *>(&e)};
-    PQXX_CHECK(
-      downcast != nullptr, "exception-to-sql_error downcast is broken.");
-    PQXX_CHECK_EQUAL(
-      downcast->query(), broken_query,
-      "Getting query from pqxx exception is broken.");
-  }
-
-  pqxx::connection conn;
-  pqxx::work tx{conn};
-  try
-  {
-    tx.exec("INVALID QUERY HERE");
-  }
-  catch (pqxx::syntax_error const &e)
-  {
-    // SQL syntax error has sqlstate error 42601.
-    PQXX_CHECK_EQUAL(
-      e.sqlstate(), "42601", "Unexpected sqlstate on syntax error.");
-  }
-}
-
-
-PQXX_REGISTER_TEST(test_exceptions);
-} // namespace