py/objstr: Skip whitespace in bytes.fromhex().

Skip whitespace characters between pairs of hex numbers.
This makes `bytes.fromhex()` compatible with cpython.

Includes simple test in `tests/basic/builtin_str_hex.py`.

Signed-off-by: Glenn Moloney <glenn.moloney@gmail.com>

tests/basics/builtin_str_hex.py

@@ -20,5 +20,20 @@ for x in (
     "08090a0b0c0d0e0f",
     "7f80ff",
     "313233344142434461626364",
+    "ab\tcd\n  ef ",
+    "ab cd ef",
+    "ab cd ef ",
+    " ab cd ef ",
+    # Invalid hex strings:
+    "abcde",  # Odd number of hex digits
+    "ab cd e",
+    "a b cd ef",  # Spaces between hex pairs
+    "ab cd e f ",
+    "abga",  # Invalid hex digits
+    "ab_cd",
+    "ab:cd",
 ):
-    print(bytes.fromhex(x))
+    try:
+        print(bytes.fromhex(x))
+    except ValueError as e:
+        print("ValueError:", e)

tests/basics/builtin_str_hex.py.exp

@@ -26,3 +26,14 @@ b'\x00\x01\x02\x03\x04\x05\x06\x07'
 b'\x08\t\n\x0b\x0c\r\x0e\x0f'
 b'\x7f\x80\xff'
 b'1234ABCDabcd'
+b'\xab\xcd\xef'
+b'\xab\xcd\xef'
+b'\xab\xcd\xef'
+b'\xab\xcd\xef'
+ValueError: non-hex digit
+ValueError: non-hex digit
+ValueError: non-hex digit
+ValueError: non-hex digit
+ValueError: non-hex digit
+ValueError: non-hex digit
+ValueError: non-hex digit