common: include filename in error message

Motivation:

If there is an IOException when reading the setup file, the corresponding
filename is not included in the message.  This may make diagnosing the
problem harder for the admin.

Modification:

Wrap the IOException to include the filename.

Result:

More useful error messages

Target: master
Requires-notes: yes
Requires-book: no
Request: 2.16
Request: 2.15
Request: 2.14
Request: 2.13
Patch: https://rb.dcache.org/r/9587/
Acked-by: Gerd Behrmann

modules/dcache/src/main/java/org/dcache/cells/UniversalSpringCell.java

@@ -310,9 +310,14 @@ private void waitForFiles()
 
     private byte[] loadSetup(File file) throws IOException, CommandException
     {
-        byte[] data = readAllBytes(file.toPath());
-        testSetup(file.toString(), data);
-        return data;
+        try {
+            byte[] data = readAllBytes(file.toPath());
+            testSetup(file.toString(), data);
+            return data;
+        } catch (IOException e) {
+            throw new IOException("Failed to read " + file + ": " +
+                    e.getMessage(), e);
+        }
     }
 
     private void testSetup(String source, byte[] data)