[SPARK-6448] Make history server log parse exceptions

This helped me to debug a parse error that was due to the event log format changing recently.

Author: Ryan Williams <[email protected]>

Closes #5122 from ryan-williams/histerror and squashes the following commits:

5831656 [Ryan Williams] line length
c3742ae [Ryan Williams] Make history server log parse exceptions

Author: ryan-williams

core/src/main/scala/org/apache/spark/deploy/history/FsHistoryProvider.scala

@@ -233,7 +233,8 @@ private[history] class FsHistoryProvider(conf: SparkConf) extends ApplicationHis
       } catch {
         case e: Exception =>
           logError(
-            s"Exception encountered when attempting to load application log ${fileStatus.getPath}")
+            s"Exception encountered when attempting to load application log ${fileStatus.getPath}",
+            e)
           None
       }
     }.toSeq.sortWith(compareAppInfo)