Cleanup: add "unreachable" message to "assert False" statements

Clarify that these blocks are unreachable so the intention is clear
if they're ever encountered.

doc/python_api/rst_from_bmesh_opdefines.py

@@ -252,8 +252,7 @@ def main():
                     name, tp = arg
                     tp_sub = None
                 else:
-                    print(arg)
-                    assert 0
+                    assert False, "unreachable, unsupported 'arg' length found %d" % len(arg)
 
                 tp_str = ""
 
@@ -322,8 +321,7 @@ def main():
                         #     but think the idea is that that pointer is for any type?
                         tp_str = ":class:`bpy.types.bpy_struct`"
                     else:
-                        print("Can't find", vars_dict_reverse[tp_sub])
-                        assert 0
+                        assert False, "unreachable, unknown type %r" % vars_dict_reverse[tp_sub]
 
                 elif tp == BMO_OP_SLOT_ELEMENT_BUF:
                     assert tp_sub is not None
@@ -362,11 +360,9 @@ def main():
                         elif tp_sub == BMO_OP_SLOT_SUBTYPE_MAP_INTERNAL:
                             tp_str += "unknown internal data, not compatible with python"
                         else:
-                            print("Can't find", vars_dict_reverse[tp_sub])
-                            assert 0
+                            assert False, "unreachable, unknown type %r" % vars_dict_reverse[tp_sub]
                 else:
-                    print("Can't find", vars_dict_reverse[tp])
-                    assert 0
+                    assert False, "unreachable, unknown type %r" % vars_dict_reverse[tp]
 
                 args_wash.append((name, default_value, tp_str, comment))
             return args_wash

scripts/modules/bpy_extras/io_utils.py

@@ -297,7 +297,7 @@ def axis_conversion(from_forward='Y', from_up='Z', to_forward='Y', to_up='Z'):
     for i, axis_lut in enumerate(_axis_convert_lut):
         if value in axis_lut:
             return Matrix(_axis_convert_matrix[i])
-    assert 0
+    assert False, "unreachable"
 
 
 def axis_conversion_ensure(operator, forward_attr, up_attr):

scripts/presets/keyconfig/keymap_data/blender_default.py

@@ -768,7 +768,7 @@ def km_window(params):
                 ("wm.search_menu", {"type": 'SPACE', "value": 'PRESS'}, None),
             )
         else:
-            assert False
+            assert False, "unreachable"
 
     return keymap
 
@@ -3530,7 +3530,7 @@ def km_frames(params):
                 ("screen.animation_play", {"type": 'SPACE', "value": 'PRESS'}, None),
             )
         else:
-            assert False
+            assert False, "unreachable"
 
         items.extend([
             ("screen.animation_play", {"type": 'SPACE', "value": 'PRESS', "shift": True, "ctrl": True},

scripts/startup/bl_operators/wm.py

@@ -2959,7 +2959,7 @@ class WM_OT_batch_rename(Operator):
                 elif method == 'SUFFIX':
                     name = name + text
                 else:
-                    assert 0
+                    assert False, "unreachable"
 
             elif ty == 'STRIP':
                 chars = action.strip_chars
@@ -3004,9 +3004,9 @@ class WM_OT_batch_rename(Operator):
                 elif method == 'TITLE':
                     name = name.title()
                 else:
-                    assert 0
+                    assert False, "unreachable"
             else:
-                assert 0
+                assert False, "unreachable"
         return name
 
     def _data_update(self, context):

tools/check_source/check_spelling.py

@@ -272,7 +272,7 @@ def words_from_text(text: str, check_type: str) -> List[Tuple[str, int]]:
             w_prev = w_lower
             w_prev_start = w_start
     else:
-        assert False
+        assert False, "unreachable"
 
     return words
 
@@ -551,7 +551,7 @@ def spell_check_file(
                 # print(filepath + ":" + str(slineno + 1) + ":" + str(scol), w, "(duplicates)")
                 yield (w, slineno, scol)
     else:
-        assert False
+        assert False, "unreachable"
 
 
 def spell_check_file_recursive(

tools/modules/blendfile.py

@@ -772,7 +772,7 @@ class BlendFileHeader:
         elif pointer_size_id == b'_':
             self.pointer_size = 4
         else:
-            assert 0
+            assert False, "unreachable"
         endian_id = values[2]
         if endian_id == b'v':
             self.is_little_endian = True
@@ -783,7 +783,7 @@ class BlendFileHeader:
             self.endian_index = 1
             self.endian_str = b'>'
         else:
-            assert 0
+            assert False, "unreachable"
 
         version_id = values[3]
         self.version = int(version_id)