Replace clear_screen() function

This is now part of wk.ansi and is fully cross-compatible.

scripts/wk/ansi.py

@@ -23,6 +23,11 @@ COLORS = {
 
 
 # Functions
+def clear_screen():
+  """Clear screen using ANSI escape."""
+  print('\033c', end='', flush=True)
+
+
 def color_string(strings, colors, sep=' '):
   """Build colored string using ANSI escapes, returns str."""
   clear_code = COLORS['CLEAR']

scripts/wk/ui/cli.py

@@ -17,7 +17,7 @@ except ImportError:
   # Assuming Python is < 3.9
   from functools import lru_cache as cache
 
-from wk.ansi import color_string, strip_colors
+from wk.ansi import clear_screen, color_string, strip_colors
 from wk.cfg.main import (
   ENABLED_UPLOAD_DATA,
   INDENT,
@@ -622,16 +622,6 @@ def choice(choices, prompt='答えろ！'):
   return answer
 
 
-def clear_screen():
-  """Simple wrapper for clear/cls."""
-  cmd = 'cls' if os.name == 'nt' else 'clear'
-  proc = subprocess.run(cmd, check=False, shell=True, stderr=subprocess.PIPE)
-
-  # Workaround for live macOS env
-  if proc.returncode != 0:
-    print('\033c')
-
-
 @cache
 def get_exception(name):
   """Get exception by name, returns exception object.