IMPALA-11976: Fix use of deprecated functions/fields removed in Python 3

Python 3 moved several things around or removed deprecated
functions / fields:
 - sys.maxint was removed, but sys.maxsize provides similar functionality
 - long was removed, but int provides the same range
 - file() was removed, but open() already provided the same functionality
 - Exception.message was removed, but str(exception) is equivalent
 - Some encodings (like hex) were moved to codecs.encode()
 - string.letters -> string.ascii_letters
 - string.lowercase -> string.ascii_lowercase
 - string.strip was removed

This fixes all of those locations. Python 3 also has slightly different
rounding behavior from round(), so this changes round() to use future's
builtins.round() to get the Python 3 behavior.

This fixes the following pylint warnings:
 - file-builtin
- long-builtin
- invalid-str-codec
- round-builtin
- deprecated-string-function
- sys-max-int
- exception-message-attribute

Testing:
 - Ran cores tests

Change-Id: I094cd7fd06b0d417fc875add401d18c90d7a792f
Reviewed-on: http://gerrit.cloudera.org:8080/19591
Reviewed-by: Joe McDonnell <joemcdonnell@cloudera.com>
Tested-by: Joe McDonnell <joemcdonnell@cloudera.com>

docker/setup_build_context.py

@@ -194,7 +194,7 @@ if args.utility_context:
 else:
   # Impala Coordinator dependencies.
   num_jars_on_classpath = 0
-  dep_classpath = file(os.path.join(IMPALA_HOME, "fe/target/build-classpath.txt")).read()
+  dep_classpath = open(os.path.join(IMPALA_HOME, "fe/target/build-classpath.txt")).read()
   for jar in dep_classpath.split(":"):
     num_jars_on_classpath += 1
     assert os.path.exists(jar), "missing jar from classpath: {0}".format(jar)
@@ -216,7 +216,7 @@ else:
   assert num_frontend_jars == 1
 
   # Impala Executor dependencies.
-  dep_classpath = file(os.path.join(IMPALA_HOME,
+  dep_classpath = open(os.path.join(IMPALA_HOME,
       "java/executor-deps/target/build-executor-deps-classpath.txt")).read()
   for jar in dep_classpath.split(":"):
     assert os.path.exists(jar), "missing jar from classpath: {0}".format(jar)