[fast-reboot-filter-routes.py] Remove click and improve error reporting (#3030)

* [fast-reboot-filter-routes.py] Remove click and improve error reporting

1. Removed click usage from a script since there is no active click
context therefore we saw these error messages:

```
ERR fast-reboot-filter-routes: Got an exception There is no active click context.: Traceback: Traceback (most recent call last):edge-core#12  File "/usr/local/bin/fast-reboot-filter-routes.py", line 18, in get_connected_routes#012    output, ret = clicommon.run_command(cmd, return_cmd=True)edge-core#12  File "/usr/local/lib/python3.9/dist-packages/utilities_common/cli.py", line 545, in run_command#012    proc = subprocess.Popen(command, shell=shell, text=True, stdout=subprocess.PIPE)edge-core#12  File "/usr/lib/python3.9/subprocess.py", line 951, in __init__#012    self._execute_child(args, executable, preexec_fn, close_fds,edge-core#12  File "/usr/lib/python3.9/subprocess.py", line 1823, in _execute_child#012    raise child_exception_type(errno_num, err_msg, err_filename)#012FileNotFoundError: [Errno 2] No such file or directory: 'sudo vtysh -c "show ip route connected json"'edge-core#12#012During handling of the above exception, another exception occurred:edge-core#12#012Traceback (most recent call last):edge-core#12  File "/usr/local/lib/python3.9/dist-packages/click/globals.py", line 23, in get_current_context#012    return getattr(_local, 'stack')[-1]#012AttributeError: '_thread._local' object has no attribute 'stack'edge-core#12#012During handling of the above exception, another exception occurred:edge-core#12#012Traceback (most recent call last):edge-core#12  File "/usr/local/bin/fast-reboot-filter-routes.py", line 79, in <module>edge-core#12    res = main()edge-core#12  File "/usr/local/bin/fast-reboot-filter-routes.py", line 70, in main#012    connected_routes = get_connected_routes()edge-core#12  File "/usr/local/bin/fast-reboot-filter-routes.py", line 27, in get_connected_routes#012    ctx = click.get_current_context()edge-core#12  File "/usr/local/lib/python3.9/dist-packages/click/globals.py", line 26, in get_current_context#012    raise RuntimeError('There is no active click context.')#012RuntimeError: There is no active click context.
```

2. Improved error reporting so that when an error occurs when we run a
command it will report it via terminal and syslog:

stdout:
```
Failed to execute sudo vtysh -c show ip route connected jsson: % Unknown command: show ip route connected jsson
```

syslog:
```
Oct 17 11:53:10.620788 arc-switch1025 ERR fast-reboot-filter-routes: Got an exception: Failed to execute sudo vtysh -c show ip route connected jsson: % Unknown command: show ip route connected jsson: Traceback: Traceback (most recent call last):edge-core#12  File "/home/admin/fast-reboot-filter-routes.py", line 73, in <module>edge-core#12    res = main()edge-core#12  File "/home/admin/fast-reboot-filter-routes.py", line 64, in main#012    connected_routes = get_connected_routes()edge-core#12  File "/home/admin/fast-reboot-filter-routes.py", line 18, in get_connected_routes#012    raise Exception("Failed to execute {}: {}".format(" ".join(cmd), output.rstrip('\n')))#012Exception: Failed to execute sudo vtysh -c show ip route connected jsson: % Unknown command: show ip route connected jsson
```

Signed-off-by: Stepan Blyschak <stepanb@nvidia.com>

* add a test for command failure

Signed-off-by: Stepan Blyschak <stepanb@nvidia.com>

* Increase coverage

Signed-off-by: Stepan Blyschak <stepanb@nvidia.com>

---------

Signed-off-by: Stepan Blyschak <stepanb@nvidia.com>

Author: stepanblyschak

scripts/fast-reboot-filter-routes.py

@@ -6,27 +6,21 @@
 import utilities_common.cli as clicommon
 import syslog
 import traceback
-import click
 from swsscommon.swsscommon import ConfigDBConnector
 
 ROUTE_IDX = 1
 
 def get_connected_routes():
     cmd = ['sudo', 'vtysh', '-c', "show ip route connected json"]
     connected_routes = []
-    try:
-        output, ret = clicommon.run_command(cmd, return_cmd=True)
-        if ret != 0:
-            click.echo(output.rstrip('\n'))
-            sys.exit(ret)
-        if output is not None:
-            route_info = json.loads(output)
-            for route in route_info.keys():
-                connected_routes.append(route)
-    except Exception:
-        ctx = click.get_current_context()
-        ctx.fail("Unable to get connected routes from bgp")
-    
+    output, ret = clicommon.run_command(cmd, return_cmd=True)
+    if ret != 0:
+        raise Exception("Failed to execute {}: {}".format(" ".join(cmd), output.rstrip('\n')))
+    if output is not None:
+        route_info = json.loads(output)
+        for route in route_info.keys():
+            connected_routes.append(route)
+
     return connected_routes
 
 def get_route(db, route):
@@ -81,6 +75,7 @@ def main():
         syslog.syslog(syslog.LOG_NOTICE, "SIGINT received. Quitting")
         res = 1
     except Exception as e:
+        print(e)
         syslog.syslog(syslog.LOG_ERR, "Got an exception %s: Traceback: %s" % (str(e), traceback.format_exc()))
         res = 2
     finally:

tests/fast_reboot_filter_routes_test.py

@@ -10,10 +10,17 @@ def setup(self):
 
     @patch('utilities_common.cli.run_command')
     def test_get_connected_routes(self, mock_run_command):
-        mock_run_command.return_value = (None, 0)
+        mock_run_command.return_value = ('{"1.1.0.0/16": {}}', 0)
         output = fast_reboot_filter_routes.get_connected_routes()
         mock_run_command.assert_called_with(['sudo', 'vtysh', '-c', "show ip route connected json"], return_cmd=True)
-        assert output == []
+        assert output == ['1.1.0.0/16']
+
+    @patch('utilities_common.cli.run_command')
+    def test_get_connected_routes_command_failed(self, mock_run_command):
+        mock_run_command.return_value = ('{"1.1.0.0/16": {}}', 1)
+        with pytest.raises(Exception):
+            fast_reboot_filter_routes.get_connected_routes()
+        mock_run_command.assert_called_with(['sudo', 'vtysh', '-c', "show ip route connected json"], return_cmd=True)
 
     def teardown(self):
         print("TEAR DOWN")