Improved exception message for failed imports

Signed-off-by: Matthias Koller <m.koller@peak-solution.de>
diff --git a/org.eclipse.mdm.apicopy/src/main/java/org/eclipse/mdm/apicopy/control/ImportTask.java b/org.eclipse.mdm.apicopy/src/main/java/org/eclipse/mdm/apicopy/control/ImportTask.java
index 2e81024..698518d 100644
--- a/org.eclipse.mdm.apicopy/src/main/java/org/eclipse/mdm/apicopy/control/ImportTask.java
+++ b/org.eclipse.mdm.apicopy/src/main/java/org/eclipse/mdm/apicopy/control/ImportTask.java
@@ -180,7 +180,7 @@
 			}
 			deleteFilesOfUploadedFileLinks();
 
-			throw new ApiCopyException("Could not copy data.", exc);
+			throw new ApiCopyException("Could not copy data: " + exc.getMessage(), exc);
 		} finally {
 			classificationUtil.clearCache();
 			clearReplacedFileLinkCache();
@@ -869,7 +869,8 @@
 					.stream().filter(q -> q.getValue(Versionable.ATTR_VERSION_STATE).extract() == VersionState.VALID)
 					.sorted(Comparator.comparing(q -> Integer.valueOf(q.getValue(Versionable.ATTR_VERSION).extract())))
 					.findFirst().orElseThrow(() -> new ApiCopyException(String
-							.format("Cannot find Quantity %s in destination!", channelSrc.getQuantity().getName())));
+							.format("Cannot find Quantity with name '%s' in destination!",
+									channelSrc.getQuantity().getName())));
 
 			Filter filter = Filter.nameOnly(etChannel, channelSrc.getName()).id(relMeasurement,
 					measurementParentDst.getID());