Add python style checking

Introduce a make recipe for flake8 to enable python
style checking. Ensure all python scripts pass flake8.
Return an error code of 0 for arcstat.py -v and
dbufstat.py -v.  Add test cases for python scripts.

Reviewed by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ian Lee <IanLee1521@gmail.com>
Closes #5230

tests/zfs-tests/tests/functional/cli_user/misc/Makefile.am

@@ -43,4 +43,7 @@ dist_pkgdata_SCRIPTS = \
 	zpool_scrub_001_neg.ksh \
 	zpool_set_001_neg.ksh \
 	zpool_status_001_neg.ksh \
-	zpool_upgrade_001_neg.ksh
+	zpool_upgrade_001_neg.ksh \
+	arcstat_001_pos.ksh \
+	arc_summary_001_pos.ksh \
+	dbufstat_001_pos.ksh

tests/zfs-tests/tests/functional/cli_user/misc/arc_summary_001_pos.ksh

@@ -0,0 +1,40 @@
+#! /bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright (c) 2015 by Lawrence Livermore National Security, LLC.
+# All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+set -A args  "" "-a" "-d" "-p 1"
+
+log_assert "arc_summary.py generates output and doesn't return an error code"
+
+typeset -i i=0
+while [[ $i -lt ${#args[*]} ]]; do
+        log_must eval "$ARC_SUMMARY ${args[i]} > /dev/null"
+        ((i = i + 1))
+done
+
+log_pass "arc_summary.py generates output and doesn't return an error code"

tests/zfs-tests/tests/functional/cli_user/misc/arcstat_001_pos.ksh

@@ -0,0 +1,41 @@
+#! /bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright (c) 2015 by Lawrence Livermore National Security, LLC.
+# All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+set -A args  "" "-s \",\"" "-x" "-v" \
+    "-f time,hit%,dh%,ph%,mh%"
+
+log_assert "arcstat.py generates output and doesn't return an error code"
+
+typeset -i i=0
+while [[ $i -lt ${#args[*]} ]]; do
+        log_must eval "$ARCSTAT ${args[i]} > /dev/null"
+        ((i = i + 1))
+done
+log_pass "arcstat.py generates output and doesn't return an error code"
+

tests/zfs-tests/tests/functional/cli_user/misc/dbufstat_001_pos.ksh

@@ -0,0 +1,40 @@
+#! /bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright (c) 2015 by Lawrence Livermore National Security, LLC.
+# All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+set -A args  "" "-b" "-d" "-r" "-v" "-s \",\"" "-x"
+
+log_assert "dbufstat.py generates output and doesn't return an error code"
+
+typeset -i i=0
+while [[ $i -lt ${#args[*]} ]]; do
+        log_must eval "$DBUFSTAT ${args[i]} > /dev/null"
+        ((i = i + 1))
+done
+
+log_pass "dbufstat.py generates output and doesn't return an error code"