code: def com_google_fonts_check_italic_angle(ttFont, style):
    
    failed = False
    value = ttFont["post"].italicAngle
  
    # Checking that italicAngle <= 0
    if value > 0:
      failed = True
      yield FAIL, Message("positive",
                          ("The value of post.italicAngle is positive, which"
                           " is likely a mistake and should become negative,"
                           " from {} to {}.").format(value, -value))
  
    # Checking that italicAngle is less than 20° (not good) or 30° (bad)
    # Also note we invert the value to check it in a clear way
    if abs(value) > 30:
      failed = True
      yield FAIL, Message("over -30 degrees",
                          ("The value of post.italicAngle ({}) is very"
                           " high (over -30°!) and should be"
                           " confirmed.").format(value))
    elif abs(value) > 20:
      failed = True
      yield WARN, Message("over -20 degrees",
                          ("The value of post.italicAngle ({}) seems very"
                           " high (over -20°!) and should be"
                           " confirmed.").format(value))
  
  
    # Checking if italicAngle matches font style:
    if "Italic" in style:
      if ttFont['post'].italicAngle == 0:
        failed = True
        yield FAIL, Message("zero-italic",
                            ("Font is italic, so post.italicAngle"
                             " should be non-zero."))
    else:
      if ttFont["post"].italicAngle != 0:
        failed = True
        yield FAIL, Message("non-zero-normal",
                            ("Font is not italic, so post.italicAngle"
                             " should be equal to zero."))
  
    if not failed:
      yield PASS, ("Value of post.italicAngle is {}"
                   " with style='{}'.").format(value, style)
docs: Checking post.italicAngle value.