tests/cpydiff/: Improve wording, add more workarounds.

tests/cpydiff/modules_sys_stdassign.py

 """
 categories: Modules,sys
-description: Override sys.stdin, sys.stdout and sys.stderr. Impossible as they are stored in read-only memory.
-cause: Unknown
+description: Overriding sys.stdin, sys.stdout and sys.stderr not possible
+cause: They are stored in read-only memory.
 workaround: Unknown
 """
 import sys

tests/cpydiff/types_bytes_keywords.py

 """
 categories: Types,bytes
-description: bytes(...) with keywords not implemented
+description: bytes() with keywords not implemented
 cause: Unknown
-workaround: Input the encoding format directly. eg. ``print(bytes('abc', 'utf-8'))``
+workaround: Pass the encoding as a positional paramter, e.g. ``print(bytes('abc', 'utf-8'))``
 """
 print(bytes('abc', encoding='utf8'))

tests/cpydiff/types_bytes_subscrstep.py

 """
 categories: Types,bytes
-description: Bytes subscr with step != 1 not implemented
-cause: Unknown
-workaround: Unknown
+description: Bytes subscription with step != 1 not implemented
+cause: MicroPython is highly optimized for memory usage.
+workaround: Use explicit loop for this very rare operation.
 """
 print(b'123'[0:3:2])

tests/cpydiff/types_exception_instancevar.py

 """
 categories: Types,Exception
-description: Assign instance variable to exception
-cause: Unknown
-workaround: Unknown
+description: User-defined attributes for builtin exceptions are not supported
+cause: MicroPython is highly optimized for memory usage.
+workaround: Use user-defined exception subclasses.
 """
 e = Exception()
 e.x = 0

tests/cpydiff/types_exception_loops.py

 """
 categories: Types,Exception
-description: While loop guards will obscure exception line number reporting due to being optimised onto the end of the code block
-cause: Unknown
+description: Exception in while loop condition may have unexpected line number
+cause: Condition checks are optimized to happen at the end of loop body, and that line number is reported.
 workaround: Unknown
 """
 l = ["-foo", "-bar"]

tests/cpydiff/types_float_rounding.py

 """
 categories: Types,float
-description: uPy and CPython outputs formats differ
+description: uPy and CPython outputs formats may differ
 cause: Unknown
 workaround: Unknown
 """

tests/cpydiff/types_int_subclassconv.py

@@ -2,7 +2,7 @@
 categories: Types,int
 description: No int conversion for int-derived types available
 cause: Unknown
-workaround: Unknown
+workaround: Avoid subclassing builtin types unless really needed. Prefer https://en.wikipedia.org/wiki/Composition_over_inheritance .
 """
 class A(int):
     __add__ = lambda self, other: A(int(self) + other)

tests/cpydiff/types_list_delete_subscrstep.py

@@ -2,7 +2,7 @@
 categories: Types,list
 description: List delete with step != 1 not implemented
 cause: Unknown
-workaround: Unknown
+workaround: Use explicit loop for this rare operation.
 """
 l = [1, 2, 3, 4]
 del l[0:4:2]

tests/cpydiff/types_list_store_subscrstep.py

@@ -2,7 +2,7 @@
 categories: Types,list
 description: List store with step != 1 not implemented
 cause: Unknown
-workaround: Unknown
+workaround: Use explicit loop for this rare operation.
 """
 l = [1, 2, 3, 4]
 l[0:4:2] = [5, 6]