Use java.lang.Error when unexpected condition occurs during rollback.

jena-db/jena-dboe-transaction/src/main/java/org/apache/jena/dboe/transaction/txn/TransactionCoordinator.java

@@ -747,8 +747,9 @@ private void executeCommitWriter(Transaction transaction, Runnable commit, Runna
                     throw new TransactionException("Exception during 'commit' - transaction rollback.", ex);
                 }
                 // Very bad. (This have been dealt with already and should get to here.)
-                SysErr.error("Transaction rollback failed. System unstable.");
-                throw new TransactionException("Exception during 'rollback' - System unstable.", ex);
+                SysErr.error("Transaction rollback failed. System unstable."+
+                    "\nPlease contact [email protected], giving details of the environment and this incident.");
+                throw new Error("Exception during 'rollback' - System unstable.", ex);
             }
             catch (Throwable ex) {
                 SysErr.warn("Unexpected Throwable during 'commit' : transaction may have committed. Attempting rollback: ",ex);

jena-tdb/src/main/java/org/apache/jena/tdb/transaction/Transaction.java

@@ -219,8 +219,9 @@ private void writerPrepareCommit() {
                 throw new TDBTransactionException("Exception during 'commit' - transaction rollback.", ex);
             }
             // Very bad. (This should not happen and have been dealt with already.)
-            SystemTDB.errlog.error("Transaction rollback failed. System unstable.");
-            throw new TDBTransactionException("Exception during 'rollback' - System unstable.", ex);
+            SystemTDB.errlog.error("Transaction rollback failed. System unstable."+
+                "\nPlease contact [email protected], giving details of the environment and this incident.");
+            throw new Error("Exception during 'rollback' - System unstable.", ex);
         }
         catch (Throwable ex) {
             SystemTDB.errlog.warn("Unexpected Throwable during 'commit' : transaction may have committed. Attempting rollback: ",ex);
@@ -302,7 +303,7 @@ public void abort() {
                 case WRITE :
                     if ( state != TxnState.ACTIVE )
                         throw new TDBTransactionException("Transaction has already committed or aborted");
-                    // Application abort. Didn't startwriing to the journal.
+                    // Application abort. Didn't start writing to the journal.
                     rollback();
                     break;
             }