font_to_py.py: Better exception text if font size > 65535 bytes.

Author: peterhinch

font_to_py.py

@@ -418,7 +418,10 @@ def append_data(data, char):
  append_data(data, self.charset[0]) # data[0] is the default char
  for char in sorted(self.keys()):
  sparse += ord(char).to_bytes(2, byteorder='little')
- sparse += (len(data)).to_bytes(2, byteorder='little') # Start
+ try:
+ sparse += (len(data)).to_bytes(2, byteorder='little') # Start
+ except OverflowError:
+ raise ValueError("Total size of font bitmap exceeds 65535 bytes.")
  append_data(data, char)
  return data, index, sparse