#57: Do not copy terminal size if the console is non-interactive to a…

…void exception

```
Traceback (most recent call last):
  File "/usr/lib/python3.8/threading.py", line 932, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.8/threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python3.8/site-packages/rkd/process.py", line 105, in push_output
    copy_terminal_size(sys.stdout, primary_fd)
  File "/usr/lib/python3.8/site-packages/rkd/process.py", line 149, in copy_terminal_size
    col, row, x_pixels, y_pixels = get_terminal_size(fd_from)
  File "/usr/lib/python3.8/site-packages/rkd/process.py", line 166, in get_terminal_size
    x = fcntl.ioctl(fd.fileno(), termios.TIOCGWINSZ, s)
OSError: [Errno 25] Inappropriate ioctl for device
```

src/rkd/process.py

@@ -102,9 +102,9 @@ def push_output(process, primary_fd, out_buffer: TextBuffer, process_state: Proc
     # terminal window size updating
     terminal_update_time = 3  # 3 seconds
     last_terminal_update = time()
-    copy_terminal_size(sys.stdout, primary_fd)
 
     if is_interactive_session:
+        copy_terminal_size(sys.stdout, primary_fd)
         to_select = [sys.stdin] + to_select
 
     while process.poll() is None: