WARNINGS --> ERRORS and improved error message

bin/pygrb/pycbc_make_offline_grb_workflow

@@ -112,7 +112,7 @@ single_ifo = wflow.cp.has_option("workflow", "allow-single-ifo-search")
 if len(sciSegs.keys()) == 0:
     plot_met = make_grb_segments_plot(wflow, segmentlistdict(), triggertime,
                                       triggername, seg_dir)
-    logging.warning("No science segments available.")
+    logging.error("No science segments available.")
     sys.exit()
 elif len(sciSegs.keys()) < 2 and not single_ifo:
     plot_met = make_grb_segments_plot(wflow, segmentlistdict(sciSegs),
@@ -121,7 +121,7 @@ elif len(sciSegs.keys()) < 2 and not single_ifo:
     msg += "If you wish to enable single IFO running add the option "
     msg += "'allow-single-ifo-search' to the [workflow] section of your "
     msg += "configuration file."
-    logging.warning(msg)
+    logging.error(msg)
     sys.exit()
 else:
     onSrc, offSrc, bufferSeg = _workflow.generate_triggered_segment(wflow,
@@ -254,8 +254,9 @@ for ifo in ifos:
     avail_segs.coalesce()
     vetoed_segs = offSrc[ifo] - avail_segs
     if onSrc[ifo].intersects(vetoed_segs):
-        logging.warning("The onsource %s overlaps with vetoed time in %s.",
-                        onSrc[ifo], ifo)
+        intersection = onSrc[ifo] & vetoed_segs
+        logging.error("The onsource %s contains the time %s that is vetoed" +
+                      " in %s.", onSrc[ifo][0][:], intersection[0][:], ifo)
         sys.exit()
 
 # Generate sky grid if needed