Centos – Unable to run Expect ” no more ptys. ” as normal user

I have an LXC container with CentOS 7.4 running.
On running expect from Normal user I am getting the below error.

user@server ~>  expect -c "spawn ls"
spawn ls
The system has no more ptys.  Ask your system administrator to create more.
    while executing
"spawn ls"

But if we execute the same from root user, It works.

[root@server]#  expect -c "spawn ls"
spawn ls

The output of mount also have these in mount point.
devpts on /dev/pts type devpts (rw,relatime,seclabel,mode=620,ptmxmode=000)

I have ran the below updates in the server.

mknod -m 600 /dev/console c 5 1 2>/dev/null
mknod -m 666 /dev/null c 1 3 2>/dev/null
mount -n -t tmpfs none /dev 2>/dev/null
mknod -m 622 /dev/console c 5 1 2>/dev/null
mknod -m 666 /dev/null c 1 3 2>/dev/null
mknod -m 666 /dev/zero c 1 5 2>/dev/null
mknod -m 666 /dev/ptmx c 5 2 2>/dev/null
mknod -m 666 /dev/tty c 5 0 2>/dev/null
mknod -m 444 /dev/random c 1 8 2>/dev/null
mknod -m 444 /dev/urandom c 1 9 2>/dev/null
chown root:tty /dev/{console,ptmx,tty} 2>/dev/null
ln -s /proc/self/fd /dev/fd 2>/dev/null
ln -s /proc/self/fd/0 /dev/stdin 2>/dev/null
ln -s /proc/self/fd/1 /dev/stdout 2>/dev/null
ln -s /proc/self/fd/2 /dev/stderr 2>/dev/null
ln -s /proc/kcore /dev/core 2>/dev/null
mkdir /dev/pts 2>/dev/null
mkdir /dev/shm 2>/dev/null
mount -t devpts -o gid=4,mode=620 none /dev/pts 2>/dev/null
mount -t tmpfs none /dev/shm 2>/dev/null
chmod 666 /dev/null

But still I am not able to run the expect command as a normal user.
I have some scripts which needs to be run as normal user with expect statements.

I have done all possible ways which I can think of. Please help!!