do not parse stderr to get correct routing stack (sonic-net#1398)

ignore the message printed on stderr

sonic:$ show ip bgp sum
usermod: Permission denied.
usermod: cannot lock /etc/passwd; try again later.
usermod: Permission denied.
usermod: cannot lock /etc/passwd; try again later.

Signed-off-by: Guohan Lu <[email protected]>

Author: lguohan

clear/main.py

@@ -78,8 +78,7 @@ def get_routing_stack():
         proc = subprocess.Popen(command,
                                 stdout=subprocess.PIPE,
                                 shell=True,
-                                text=True,
-                                stderr=subprocess.STDOUT)
+                                text=True)
         stdout = proc.communicate()[0]
         proc.wait()
         result = stdout.rstrip('\n')

show/main.py

@@ -57,8 +57,7 @@ def get_routing_stack():
         proc = subprocess.Popen(command,
                                 stdout=subprocess.PIPE,
                                 shell=True,
-                                text=True,
-                                stderr=subprocess.STDOUT)
+                                text=True)
         stdout = proc.communicate()[0]
         proc.wait()
         result = stdout.rstrip('\n')