Handling deletion of Port Channel before deletion of its members

config/main.py

@@ -1230,7 +1230,10 @@ def add_portchannel(ctx, portchannel_name, min_links, fallback):
 def remove_portchannel(ctx, portchannel_name):
     """Remove port channel"""
     db = ctx.obj['db']
-    db.set_entry('PORTCHANNEL', portchannel_name, None)
+    if len([(k, v) for k, v in db.get_table('PORTCHANNEL_MEMBER') if k == portchannel_name]) != 0:
+        click.echo("Error: Portchannel {} contains members. Remove members before deleting Portchannel!".format(portchannel_name))
+    else:
+        db.set_entry('PORTCHANNEL', portchannel_name, None)
 
 @portchannel.group(cls=clicommon.AbbreviationGroup, name='member')
 @click.pass_context

doc/Command-Reference.md

@@ -4838,6 +4838,8 @@ Command takes two optional arguements given below.
 1) min-links  - minimum number of links required to bring up the portchannel
 2) fallback - true/false. LACP fallback feature can be enabled / disabled.  When it is set to true, only one member port will be selected as active per portchannel during fallback mode. Refer https://github.com/Azure/SONiC/blob/master/doc/lag/LACP%20Fallback%20Feature%20for%20SONiC_v0.5.md for more details about fallback feature.
 
+A port channel can be deleted only if it does not have any members or the members are already deleted. When a user tries to delete a port channel and the port channel still has one or more members that exist, the deletion of port channel is blocked. 
+
 - Usage:
   ```
   config portchannel (add | del) <portchannel_name> [min-links <num_min_links>] [fallback (true | false)]