IMPALA-11952 (part 2): Fix print function syntax

Python 3 now treats print as a function and requires
the parenthesis in invocation.

print "Hello World!"
is now:
print("Hello World!")

This fixes all locations to use the function
invocation. This is more complicated when the output
is being redirected to a file or when avoiding the
usual newline.

print >> sys.stderr , "Hello World!"
is now:
print("Hello World!", file=sys.stderr)

To support this properly and guarantee equivalent behavior
between python 2 and python 3, all files that use print
now add this import:
from __future__ import print_function

This also fixes random flake8 issues that intersect with
the changes.

Testing:
 - check-python-syntax.sh shows no errors related to print

Change-Id: Ib634958369ad777a41e72d80c8053b74384ac351
Reviewed-on: http://gerrit.cloudera.org:8080/19552
Reviewed-by: Joe McDonnell <joemcdonnell@cloudera.com>
Reviewed-by: Michael Smith <michael.smith@cloudera.com>
Tested-by: Michael Smith <michael.smith@cloudera.com>

lib/python/impala_py_lib/gdb/impala-gdb.py

@@ -19,6 +19,7 @@
 # A collection of useful Python GDB modules and commands for
 # debugging Impala core dumps.
 #
+from __future__ import print_function
 import gdb
 from collections import defaultdict