Removed Python 2 and Python 3.5- support

Deprecation of Python versions below 3.6 gives opportunity to unify the
build and install requirements for OpenZFS packages. The minimal
supported Python version is 3.6 as this is the most recent Python
package CentOS/RHEL 7 users can get.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Rich Ercolani <rincebrain@gmail.com>
Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Signed-off-by: szubersk <szuberskidamian@gmail.com>
Closes #12925

tests/test-runner/bin/test-runner.py.in

@@ -15,19 +15,14 @@
 # Copyright (c) 2012, 2018 by Delphix. All rights reserved.
 # Copyright (c) 2019 Datto Inc.
 #
-# This script must remain compatible with Python 2.6+ and Python 3.4+.
+# This script must remain compatible with Python 3.6+.
 #
 
-# some python 2.7 system don't have a configparser shim
-try:
-    import configparser
-except ImportError:
-    import ConfigParser as configparser
-
 import os
 import sys
 import ctypes
 import re
+import configparser
 
 from datetime import datetime
 from optparse import OptionParser
@@ -37,7 +32,7 @@ from select import select
 from subprocess import PIPE
 from subprocess import Popen
 from threading import Timer
-from time import time
+from time import time, CLOCK_MONOTONIC_RAW
 
 BASEDIR = '/var/tmp/test_results'
 TESTDIR = '/usr/share/zfs/'
@@ -49,9 +44,6 @@ LOG_OUT = 'LOG_OUT'
 LOG_ERR = 'LOG_ERR'
 LOG_FILE_OBJ = None
 
-# some python 2.7 system don't have a concept of monotonic time
-CLOCK_MONOTONIC_RAW = 4  # see <linux/time.h>
-
 
 class timespec(ctypes.Structure):
     _fields_ = [

tests/test-runner/bin/zts-report.py.in

@@ -15,7 +15,7 @@
 # Copyright (c) 2017 by Delphix. All rights reserved.
 # Copyright (c) 2018 by Lawrence Livermore National Security, LLC.
 #
-# This script must remain compatible with Python 2.6+ and Python 3.4+.
+# This script must remain compatible with Python 3.6+.
 #
 
 import os
@@ -62,13 +62,13 @@ known_reason = 'Known issue'
 exec_reason = 'Test user execute permissions required for utilities'
 
 #
-# Some tests require a minimum python version of 3.5 and will be skipped when
+# Some tests require a minimum python version of 3.6 and will be skipped when
 # the default system version is too old.  There may also be tests which require
-# additional python modules be installed, for example python-cffi is required
+# additional python modules be installed, for example python3-cffi is required
 # by the pyzfs tests.
 #
-python_reason = 'Python v3.5 or newer required'
-python_deps_reason = 'Python modules missing: python-cffi'
+python_reason = 'Python v3.6 or newer required'
+python_deps_reason = 'Python modules missing: python3-cffi'
 
 #
 # Some tests require the O_TMPFILE flag which was first introduced in the