Failed to execute SCP in SSH

Here I provide full details with script etails:

I am running my script in HUB1.

First, by asking users for credentials like username, password, filename, path.

Snipet example:

try:
    usrname = raw_input('Enter your credentials:')
    regex = r'[x][A-Za-z]{6,6}'
    sigMatch = re.match(regex,usrname)      --> username & pattern matching
    sigMatch.group()

except AttributeError:
    print "Kindly enter your name"
    raise AttributeError

   [...]

      

        
        
        
      

    

Immediately I do SSH from HUB1 like below:

ssh.load_system_host_keys()
ssh.connect('100.103.113.15', username='', password='')
ssh_stdin, ssh_stdout, ssh_stderr = ssh.exec_command("cd /home/dir;ls -lrt")

      

        
        
        
      

    

By ssh from HUB1, I can actually log into HUB2 and copy the file to the desired directory [i, e, although I run my script in H1 via SSH, I can go through HUB2 and execute commands in H2 and perform the desired Operations]

Now the Challenge is gone:

Now I need to copy the same file from HUB2 to HUB3 [which I copied from Hub1] by running the same script in Hub1 as myself. So I did scp in SSH like below:

ssh_stdin,ssh_stdout, ssh_stderr = ssh.exec_command("scp %s 
usrname@112.186.104.7:/home/dir/ABCdir" %(imageName))

      

        
        
        
      

    

Here you need to ask for a password for the user, for example . Enter your password , but above the command, the ssh_stderr query statement directs a pipe. Because of this, I cannot successfully copy the file when I scp in ssh.exec_command ("").

Points to remember:

• I don't want to run two scripts one in H1 and the other in H2 (for scp) ---> excluded

• My intention is to copy the file from h1 -> h2 -> h3, which are independent of each other.

I followed the following procedure and in addition to this I tried a couple of methods

• adding unknown_host_key [by executing this input, output and error channels are open, but no file transfer occurs]

• Calling another script in HUB2 [I can call scripts that don't require user input, but my goal is to give the user input. So it failed to call another script here].

I ask you to provide possible ways to eliminate the above problem.