Error if trying to change divisor after object creation.

Author: domdfcoding

locale/circuitpython.pot

@@ -3127,7 +3127,7 @@ msgid "division by zero"
 msgstr ""
 
 #: ports/espressif/common-hal/rotaryio/IncrementalEncoder.c
-msgid "divisor must be 4"
+msgid "divisor cannot be changed after object creation"
 msgstr ""
 
 #: extmod/ulab/code/numpy/vector.c

ports/espressif/common-hal/rotaryio/IncrementalEncoder.c

@@ -135,5 +135,5 @@ mp_int_t common_hal_rotaryio_incrementalencoder_get_divisor(rotaryio_incremental
 }
 
 void common_hal_rotaryio_incrementalencoder_set_divisor(rotaryio_incrementalencoder_obj_t *self, mp_int_t divisor) {
-    self->divisor = divisor;
+    mp_raise_ValueError(translate("divisor cannot be changed after object creation"));
 }