[tests] Do not trim from PATH if we did not append to it; Clean up/fix shebangs in scripts (sonic-net#1233)

Some tests were trimming the last item from system PATH, but they never appended anything to it, thus these tests were trimming valid entries from the tail of the system path, which in turn caused scripts with shebangs like `#!/usr/bin/env python` to fail, because once `/usr/bin` was removed from PATH, `python` could not be found.

**- How I did it**

- Remove lines which trimmed the last entry from system PATH in the teardown function if nothing was appended to PATH in the setup method.
- Remove shebangs from non-executable Python files
- Fix shebangs which had a space in them
- Replace `#!/usr/bin/python` shebangs with the preferred, more portable `#!/usr/bin/env python` in executable scripts

Author: jleveque

clear/main.py

@@ -1,5 +1,3 @@
-#! /usr/bin/python -u
-
 import click
 import os
 import subprocess

config/kube.py

@@ -1,6 +1,3 @@
-#!/usr/bin/python -u
-# -*- coding: utf-8 -*-
-
 import fcntl
 import os
 import shutil

connect/main.py

@@ -1,5 +1,3 @@
-#! /usr/bin/python -u
-
 import click
 import os
 import pexpect

counterpoll/main.py

@@ -1,5 +1,3 @@
-#! /usr/bin/python -u
-
 import click
 import json
 import swsssdk

debug/main.py

@@ -1,6 +1,3 @@
-#! /usr/bin/python -u
-# date: 07/12/17
-
 import click
 import subprocess
 

pfcwd/main.py

@@ -1,5 +1,3 @@
-#! /usr/bin/python -u
-
 import os
 import sys
 

scripts/aclshow

@@ -1,4 +1,5 @@
-#!/usr/bin/python
+#!/usr/bin/env python
+
 """
 using aclshow to display SONiC switch acl rules and counters
 

scripts/dump_nat_entries.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 
 """"
 Description: dump_nat_entries.py -- dump conntrack nat entries from kernel into a file

scripts/ecnconfig

@@ -1,4 +1,5 @@
-#!/usr/bin/python
+#!/usr/bin/env python
+
 """
 ecnconfig is the utility to
 

scripts/fanshow

@@ -1,4 +1,5 @@
-#!/usr/bin/python
+#!/usr/bin/env python
+
 """
     Script to show fan status.
 """

scripts/fdbclear

@@ -1,4 +1,5 @@
-#!/usr/bin/python
+#!/usr/bin/env python
+
 """
     Script to clear MAC/FDB entries learnt in Hardware
 

scripts/fdbshow

@@ -1,4 +1,5 @@
-#!/usr/bin/python
+#!/usr/bin/env python
+
 """
     Script to show MAC/FDB entries learnt in Hardware
     

scripts/gearboxutil

@@ -1,4 +1,4 @@
-#! /usr/bin/python
+#!/usr/bin/env python
 
 import swsssdk
 import sys

scripts/intfutil

@@ -1,4 +1,4 @@
-#! /usr/bin/python
+#!/usr/bin/env python
 
 import argparse
 import os

scripts/mmuconfig

@@ -1,4 +1,5 @@
-#!/usr/bin/python
+#!/usr/bin/env python
+
 """
 mmuconfig is the utility to show and change mmu configuration
 

scripts/natclear

@@ -1,4 +1,5 @@
-#!/usr/bin/python
+#!/usr/bin/env python
+
 """
     Script to clear nat dynamic entries from Hardware and also to clear the nat statistics
 

scripts/natconfig

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 
 """
     Script to show nat configuration 

scripts/natshow

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 
 """
     Script to show nat entries and nat statistics in a summary view

scripts/nbrshow

@@ -1,4 +1,5 @@
-#!/usr/bin/python
+#!/usr/bin/env python
+
 """
     Script to show Ipv4/Ipv6 neighbor entries
 

scripts/portconfig

@@ -1,4 +1,5 @@
-#!/usr/bin/python
+#!/usr/bin/env python
+
 """
 portconfig is the utility to show and change ECN configuration
 

scripts/psushow

@@ -1,4 +1,4 @@
-#! /usr/bin/python
+#!/usr/bin/env python
 
 import argparse
 import sys

scripts/sfpshow

@@ -1,4 +1,5 @@
-#!/usr/bin/python
+#!/usr/bin/env python
+
 """
     Script to show sfp eeprom and presence status.
     Not like sfputil this scripts get the sfp data from DB directly.

scripts/sonic-kdump-config

@@ -1,4 +1,5 @@
-#!/usr/bin/python
+#!/usr/bin/env python
+
 '''
 Copyright 2019 Broadcom. The term "Broadcom" refers to Broadcom Inc.
 and/or its subsidiaries.

scripts/sonic_sku_create.py

@@ -1,4 +1,5 @@
-#!/usr/bin/python
+#!/usr/bin/env python
+
 """
 usage: sonic_sku_create.py [-h] [-v] [-f FILE] [-m [MINIGRAPH_FILE]] [-b BASE]
                            [-r] [-k HWSKU]

scripts/tempershow

@@ -1,4 +1,5 @@
-#!/usr/bin/python
+#!/usr/bin/env python
+
 """
     Script to show fan status.
 """

scripts/watermarkstat

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 
 #####################################################################
 #

show/kube.py

@@ -1,6 +1,3 @@
-#!/usr/bin/python -u
-# -*- coding: utf-8 -*-
-
 import os
 
 import click

show/main.py

@@ -1,5 +1,3 @@
-#! /usr/bin/python -u
-
 import json
 import netaddr
 import os

sonic_installer/main.py

@@ -1,5 +1,3 @@
-#! /usr/bin/python -u
-
 try:
     import ConfigParser as configparser
 except ImportError:

tests/crm_test.py

@@ -999,7 +999,6 @@ def test_crm_show_resources_nexthop(self):
     @classmethod
     def teardown_class(cls):
         print("TEARDOWN")
-        os.environ["PATH"] = os.pathsep.join(os.environ["PATH"].split(os.pathsep)[:-1])
         os.environ["UTILITIES_UNIT_TESTING"] = "0"
 
 class TestCrmMultiAsic(object):
@@ -1295,7 +1294,6 @@ def test_crm_multi_asic_show_resources_nexthop(self):
     @classmethod
     def teardown_class(cls):
         print("TEARDOWN")
-        os.environ["PATH"] = os.pathsep.join(os.environ["PATH"].split(os.pathsep)[:-1])
         os.environ["UTILITIES_UNIT_TESTING"] = "0"
         os.environ["UTILITIES_UNIT_TESTING_TOPOLOGY"] = ""
         import mock_tables.mock_single_asic

tests/sflow_test.py

@@ -267,5 +267,4 @@ def test_config_sflow_intf_sample_rate(self):
     @classmethod
     def teardown_class(cls):
         print("TEARDOWN")
-        os.environ["PATH"] = os.pathsep.join(os.environ["PATH"].split(os.pathsep)[:-1])
         os.environ["UTILITIES_UNIT_TESTING"] = "0"

tests/show_breakout_test.py

@@ -61,5 +61,4 @@ def test_single_intf_current_mode(self):
     @classmethod
     def teardown_class(cls):
         print("TEARDOWN")
-        os.environ["PATH"] = os.pathsep.join(os.environ["PATH"].split(os.pathsep)[:-1])
         os.environ["UTILITIES_UNIT_TESTING"] = "0"

tests/show_platform_test.py

@@ -54,5 +54,4 @@ def test_summary(self):
     @classmethod
     def teardown_class(cls):
         print("TEARDOWN")
-        os.environ["PATH"] = os.pathsep.join(os.environ["PATH"].split(os.pathsep)[:-1])
         os.environ["UTILITIES_UNIT_TESTING"] = "0"

tests/system_health_test.py

@@ -1,5 +1,3 @@
-#! /usr/bin/python -u
-
 import sys
 import os
 

undebug/main.py

@@ -1,6 +1,3 @@
-#! /usr/bin/python -u
-# date: 07/12/17
-
 import click
 import subprocess