cqlsh should return a non-zero error code if a query fails

patch by Branden Visser and Mikhail Stepura; reviewed by Mikhail Stepura for CASSANDRA-6344

CHANGES.txt

@@ -23,6 +23,7 @@
  * remove duplicate query for local tokens (CASSANDRA-7182)
  * raise streaming phi convict threshold level (CASSANDRA-7063)
  * reduce garbage creation in calculatePendingRanges (CASSANDRA-7191)
+ * exit CQLSH with error status code if script fails (CASSANDRA-6344)
 
 1.2.16
  * Add UNLOGGED, COUNTER options to BATCH documentation (CASSANDRA-6816)

bin/cqlsh

@@ -548,6 +548,7 @@ class Shell(cmd.Cmd):
             self.show_line_nums = True
         self.stdin = stdin
         self.query_out = sys.stdout
+        self.statement_error = False
 
     def set_expanded_cql_version(self, ver):
         ver, vertuple = full_cql_version(ver)
@@ -2175,6 +2176,7 @@ class Shell(cmd.Cmd):
         self.query_out.flush()
 
     def printerr(self, text, color=RED, newline=True, shownum=None):
+        self.statement_error = True
         if shownum is None:
             shownum = self.show_line_nums
         if shownum:
@@ -2404,6 +2406,8 @@ def main(options, hostname, port):
 
     shell.cmdloop()
     save_history()
+    if options.file and shell.statement_error:
+        sys.exit(2)
 
 if __name__ == '__main__':
     main(*read_options(sys.argv[1:], os.environ))