[SPARK-12120][PYSPARK] Improve exception message when failing to init…

…ialize HiveContext in PySpark

davies Mind to review ?

This is the error message after this PR

```
15/12/03 16:59:53 WARN ObjectStore: Failed to get database default, returning NoSuchObjectException
/Users/jzhang/github/spark/python/pyspark/sql/context.py:689: UserWarning: You must build Spark with Hive. Export 'SPARK_HIVE=true' and run build/sbt assembly
  warnings.warn("You must build Spark with Hive. "
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/jzhang/github/spark/python/pyspark/sql/context.py", line 663, in read
    return DataFrameReader(self)
  File "/Users/jzhang/github/spark/python/pyspark/sql/readwriter.py", line 56, in __init__
    self._jreader = sqlContext._ssql_ctx.read()
  File "/Users/jzhang/github/spark/python/pyspark/sql/context.py", line 692, in _ssql_ctx
    raise e
py4j.protocol.Py4JJavaError: An error occurred while calling None.org.apache.spark.sql.hive.HiveContext.
: java.lang.RuntimeException: java.net.ConnectException: Call From jzhangMBPr.local/127.0.0.1 to 0.0.0.0:9000 failed on connection exception: java.net.ConnectException: Connection refused; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused
	at org.apache.hadoop.hive.ql.session.SessionState.start(SessionState.java:522)
	at org.apache.spark.sql.hive.client.ClientWrapper.<init>(ClientWrapper.scala:194)
	at org.apache.spark.sql.hive.client.IsolatedClientLoader.createClient(IsolatedClientLoader.scala:238)
	at org.apache.spark.sql.hive.HiveContext.executionHive$lzycompute(HiveContext.scala:218)
	at org.apache.spark.sql.hive.HiveContext.executionHive(HiveContext.scala:208)
	at org.apache.spark.sql.hive.HiveContext.functionRegistry$lzycompute(HiveContext.scala:462)
	at org.apache.spark.sql.hive.HiveContext.functionRegistry(HiveContext.scala:461)
	at org.apache.spark.sql.UDFRegistration.<init>(UDFRegistration.scala:40)
	at org.apache.spark.sql.SQLContext.<init>(SQLContext.scala:330)
	at org.apache.spark.sql.hive.HiveContext.<init>(HiveContext.scala:90)
	at org.apache.spark.sql.hive.HiveContext.<init>(HiveContext.scala:101)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
	at py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:234)
	at py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:381)
	at py4j.Gateway.invoke(Gateway.java:214)
	at py4j.commands.ConstructorCommand.invokeConstructor(ConstructorCommand.java:79)
	at py4j.commands.ConstructorCommand.execute(ConstructorCommand.java:68)
	at py4j.GatewayConnection.run(GatewayConnection.java:209)
	at java.lang.Thread.run(Thread.java:745)
```

Author: Jeff Zhang <zjffdu@apache.org>

Closes #10126 from zjffdu/SPARK-12120.

python/pyspark/sql/context.py

@@ -15,6 +15,7 @@
 # limitations under the License.
 #
 
+from __future__ import print_function
 import sys
 import warnings
 import json
@@ -571,9 +572,10 @@ class HiveContext(SQLContext):
                 self._scala_HiveContext = self._get_hive_ctx()
             return self._scala_HiveContext
         except Py4JError as e:
-            raise Exception("You must build Spark with Hive. "
-                            "Export 'SPARK_HIVE=true' and run "
-                            "build/sbt assembly", e)
+            print("You must build Spark with Hive. "
+                  "Export 'SPARK_HIVE=true' and run "
+                  "build/sbt assembly", file=sys.stderr)
+            raise
 
     def _get_hive_ctx(self):
         return self._jvm.HiveContext(self._jsc.sc())