I am running Fabric 1.6.0 (paramiko 1.10.1). I have the following script:

```
from fabric.api import env, output, run, sudo

user='your-user'
host='your-server'
port='your-port'
command = 'ps -ef'

output['running']  = False     # Avoid fabric to output what it is doing behind the scenes
output['stdout']   = False     # Do not show stdout
output['stderr']   = False     # Do not show stderr
output['status']   = False     # Prevent fabric from using print in some situations (at least in disconnect_all)
output['warnings'] = False     # Avoid fabric from showing messages about failed commands

def run_it(command, user, host, port, keyfile):
    env.host_string = "%s@%s:%s" % (user, host, port)
    env.key_filename = keyfile
    try:
        res = run(command, pty=False, shell=True)
        print "SUCCESS: return_code=%s" % (return_code)
    except Exception, e:
        print "ERROR  : %s" % (e)
        stdout, return_code =  None, None
    return stdout, return_code

run_it(command, user, host, port, '/bad/keyfile')
run_it(command, user, host, port, '/home/gonvaled/.ssh/id_rsa')
run_it(command, user, host, port, '/bad/keyfile')

```

This outputs:

```
ERROR  : [Errno 2] No such file or directory: '/bad/keyfile'
SUCCESS: return_code=0
SUCCESS: return_code=0

```

But I expected:

```
ERROR  : [Errno 2] No such file or directory: '/bad/keyfile'
SUCCESS: return_code=0
ERROR  : [Errno 2] No such file or directory: '/bad/keyfile'

```

Why is this happening? It seems the good keyfile is being *remembered*? Why? This is annoying, because it shows that I can not set the keyfile on the fly, so I am not sure which one is being used: the first I set, the second I set? What is the criteria to choose it? How many are remembered? ...

I am using fabric as an ssh library (not in fabfiles), so I am calling it with different parameters. I rely on the `env` to pass those parameters to fabric. This is mostly working fine, but `key_filename` seems to be an exception.