dest service use .bashrc to change python version ,open sftp error

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when the remote PC use ~/.bashrc to change python version
s.open_sftp() while report a error:
SFTPError: Garbage packet received

remote PC ~/.bashrc like this:
$source ~/.pythonbrew/etc/bashrc
$pythonbrew use 2.6.7

code like this:
s = paramiko.SSHClient()
s.load_system_host_keys()
s.set_missing_host_key_policy(paramiko.AutoAddPolicy())
s.connect(ip, port, username, password)
s.open_sftp() # get error at here

if I made remote PC ~/.bashrc like this:
#source ~/.pythonbrew/etc/bashrc
#pythonbrew use 2.6.7
then no error