no Exception for precondition file, better error formatting

ws/Unitmarking/src/main/java/de/hdm_stuttgart/mi/unitmarking/xsd/InstanceTest.java

@@ -128,8 +128,10 @@ public class InstanceTest {
             log.info("Precondition file '" + preconditionValidFilename.get() + "' is valid");
             preconditionSucceeded = true;            
          } catch (final SAXException e) {
-            tmpPreconditionErrMsg = "Instance " + xmlInstance + ": Precondition file " + preconditionValidFilename.get() + " is invalid:" + e.getMessage();
-            log.info(tmpPreconditionErrMsg + ": " + e.getCause() + ":" + e.getMessage(), e);
+            tmpPreconditionErrMsg = "Instance " + xmlInstance +
+                  ":\n  Precondition file »" + preconditionValidFilename.get() + "« is invalid:\n  " + 
+            e.getMessage() + "\n ";
+            log.info(tmpPreconditionErrMsg + ": " + e.getCause() + ":" + e.getMessage());
          } catch (final IOException e) {
             tmpPreconditionErrMsg = "Instance '" + xmlInstance + ": Precondition file '" + preconditionValidFilename.get() + "' cannot be read:" + e.getMessage();
             log.info(tmpPreconditionErrMsg, e);