IMPALA-9627: Update utility scripts for Python 3 (part 2)

We're starting to see environments where the system Python ('python') is
Python 3. Updates utility and build scripts to work with Python 3, and
updates check-pylint-py3k.sh to check scripts that use system python.

Fixes other issues found during a full build and test run with Python
3.8 as the default for 'python'.

Fixes a impala-shell tip that was supposed to have been two tips (and
had no space after period when they were printed).

Removes out-of-date deploy.py and various Python 2.6 workarounds.

Testing:
- Full build with /usr/bin/python pointed to python3
- run-all-tests passed with python pointed to python3
- ran push_to_asf.py

Change-Id: Idff388aff33817b0629347f5843ec34c78f0d0cb
Reviewed-on: http://gerrit.cloudera.org:8080/19697
Reviewed-by: Michael Smith <michael.smith@cloudera.com>
Tested-by: Michael Smith <michael.smith@cloudera.com>

infra/python/deps/download_requirements

@@ -22,7 +22,6 @@ set -euo pipefail
 DIR="$(dirname "$0")"
 
 pushd "$DIR"
-PY26="$(./find_py26.py)"
 # Directly download packages listed in *requirements.txt, but don't install them.
-"$PY26" pip_download.py
+./pip_download.py
 popd

infra/python/deps/find_py26.py

@@ -1,47 +0,0 @@
-#!/usr/bin/python
-#
-# Licensed to the Apache Software Foundation (ASF) under one
-# or more contributor license agreements.  See the NOTICE file
-# distributed with this work for additional information
-# regarding copyright ownership.  The ASF licenses this file
-# to you under the Apache License, Version 2.0 (the
-# "License"); you may not use this file except in compliance
-# with the License.  You may obtain a copy of the License at
-#
-#   http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing,
-# software distributed under the License is distributed on an
-# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
-# KIND, either express or implied.  See the License for the
-# specific language governing permissions and limitations
-# under the License.
-
-# This script finds Python 2.6 or higher on the system and outputs the
-# system command to stdout. The script exits with a nonzero exit code if
-# Python 2.6+ is not present.
-
-from __future__ import print_function
-import os
-import subprocess
-import sys
-import textwrap
-
-def detect_python_cmd():
-  '''Returns the system command that provides python 2.6 or greater.'''
-  paths = os.getenv("PATH").split(os.path.pathsep)
-  for cmd in ("python", "python27", "python2.7", "python-27", "python-2.7", "python26",
-      "python2.6", "python-26", "python-2.6"):
-    for path in paths:
-      cmd_path = os.path.join(path, cmd)
-      if not os.path.exists(cmd_path) or not os.access(cmd_path, os.X_OK):
-        continue
-      exit = subprocess.call([cmd_path, "-c", textwrap.dedent("""
-          import sys
-          sys.exit(int(sys.version_info[:2] < (2, 6)))""")])
-      if exit == 0:
-        return cmd_path
-  raise Exception("Could not find minimum required python version 2.6")
-
-
-print(detect_python_cmd())

infra/python/deps/pip_download.py

@@ -19,9 +19,9 @@
 
 # Implement the basic 'pip download' functionality in a way that gives us more control
 # over which archive type is downloaded and what post-download steps are executed.
-# This script requires Python 2.6+.
+# This script requires Python 2.7+.
 
-from __future__ import print_function
+from __future__ import absolute_import, division, print_function
 import hashlib
 import multiprocessing.pool
 import os