Tests for unicode identifiers (#2816)

fuzz.py

@@ -48,7 +48,7 @@ def test_idempotent_any_syntatically_valid_python(
         dst_contents = black.format_str(src_contents, mode=mode)
     except black.InvalidInput:
         # This is a bug - if it's valid Python code, as above, Black should be
-        # able to cope with it.  See issues #970, #1012, #1358, and #1557.
+        # able to cope with it.  See issues #970, #1012
         # TODO: remove this try-except block when issues are resolved.
         return
     except TokenError as e:

tests/data/tricky_unicode_symbols.py

@@ -4,3 +4,6 @@
 x󠄀 = 4
 មុ = 1
 Q̇_per_meter = 4
+
+A᧚ = 3
+A፩ = 8