cli: ignore EINTR caused by SIGWINCH when calling poll()

[yousong]

This can happen when adjusting a tmux pane running mininet cli. The
process will receive SIGWINCH causing the poll() call to raise
select.error

Below is a session dump with strace

09:55:52.498106 poll([{fd=0, events=POLLIN}, {fd=28, events=POLLIN}], 2, -1) = ? ERESTART_RESTARTBLOCK (Interrupted by signal)
09:55:52.606734 --- SIGWINCH {si_signo=SIGWINCH, si_code=SI_KERNEL} ---
09:55:52.606770 rt_sigreturn({mask=[]}) = -1 EINTR (Interrupted system call)
Traceback (most recent call last):
  File "examples/topofac.py", line 527, in <module>
    run()
  File "examples/topofac.py", line 522, in run
    CLI( net )
  File "/home/yunion/git-repo/mininet/mininet/cli.py", line 68, in __init__
    self.run()
  File "/home/yunion/git-repo/mininet/mininet/cli.py", line 103, in run
    self.cmdloop()
  File "/home/yunion/.usr/lib/python2.7/cmd.py", line 142, in cmdloop
    stop = self.onecmd(line)
  File "/home/yunion/.usr/lib/python2.7/cmd.py", line 220, in onecmd
    return self.default(line)
  File "/home/yunion/git-repo/mininet/mininet/cli.py", line 422, in default
    self.waitForNode( node )
  File "/home/yunion/git-repo/mininet/mininet/cli.py", line 440, in waitForNode
    bothPoller.poll()
select.error: (4, 'Interrupted system call')
09:55:52.622076 rt_sigaction(SIGINT, {SIG_DFL, [], SA_RESTORER, 0x7ff9a9b936d0}, {0x7ff9a9ef2230, [], SA_RESTORER, 0x7ff9a9b936d0}, 8) = 0
09:55:52.631905 +++ exited with 1 +++

[yousong]

v2 <- v1 Disable pylint check unpacking-non-sequence for the line unpacking select.error

[lantz]

Could you remove the unnecessary changes caused by deleting from select import ... ?

[lantz]

There is no reason to delete this. Better to preserve the style of the code and add the additional things you need.

[yousong]

v3 <- v2 import select without touching from select import xx

[lantz]

Great, thanks!