llvmbot monitor: Highlight in red time since if it is > 1 day

No build should be taking that long so it probably means
an offline machine or lost connection to the buildmaster.

Change-Id: I6f84c6e4d8a7f1d0c5f57ec2c2b982e5f97f655a
diff --git a/monitor/bot-status.py b/monitor/bot-status.py
index 730442f..2f553ea 100755
--- a/monitor/bot-status.py
+++ b/monitor/bot-status.py
@@ -227,7 +227,15 @@
                            'FAIL' if status['fail'] else 'PASS'))
         empty_cell="  <td>&nbsp;</td>\n"
         if 'time_since' in status:
-          temp.write("  <td>{}</td>\n".format(status['time_since']))
+          time_since = status['time_since']
+          # No build should be taking more than a day
+          if time_since > timedelta(hours=24):
+              time_since = "<p style=\"color:red\">{}</p>".format(
+                      time_since)
+          else:
+              time_since = str(time_since)
+
+          temp.write("  <td>{}</td>\n".format(time_since))
         else:
           temp.write(empty_cell)
         if 'duration' in status: