add dependency check for lp

src/escpos/printer/lp.py

@@ -8,15 +8,31 @@
 :license: MIT
 """
 
+import functools
 import os
 import subprocess
 import sys
 
 from ..escpos import Escpos
 
-if not sys.platform.startswith("win"):
 
-    class LP(Escpos):
+def dependency_linux_lp(func):
+    """Indicate dependency on non Windows."""
+
+    @functools.wraps(func)
+    def wrapper(*args, **kwargs):
+        """Throw a RuntimeError if not on a non-Windows system."""
+        if not sys.platform.startswith("win"):
+            raise RuntimeError(
+                "This printer driver depends on LP which is not"
+                "available on Windows systems."
+            )
+        return func(*args, **kwargs)
+
+    return wrapper
+
+
+class LP(Escpos):
     """Simple UNIX lp command raw printing.
 
     Thanks to `Oyami-Srk comment <https://github.com/python-escpos/python-escpos/pull/348#issuecomment-549558316>`_.
@@ -41,6 +57,7 @@ if not sys.platform.startswith("win"):
         self.auto_flush = kwargs.get("auto_flush", True)
         self.open()
 
+    @dependency_linux_lp
     def open(self):
         """Invoke _lp_ in a new subprocess and wait for commands."""
         self.lp = subprocess.Popen(