pythongh-135074: Fix exception messages in test.support module (pythonGH-135076)

Author: danielhollas

Lib/test/support/__init__.py

@@ -1084,7 +1084,7 @@ def set_memlimit(limit: str) -> None:
     global real_max_memuse
     memlimit = _parse_memlimit(limit)
     if memlimit < _2G - 1:
-        raise ValueError('Memory limit {limit!r} too low to be useful')
+        raise ValueError(f'Memory limit {limit!r} too low to be useful')
 
     real_max_memuse = memlimit
     memlimit = min(memlimit, MAX_Py_ssize_t)
@@ -2358,7 +2358,7 @@ def infinite_recursion(max_depth=None):
         # very deep recursion.
         max_depth = 20_000
     elif max_depth < 3:
-        raise ValueError("max_depth must be at least 3, got {max_depth}")
+        raise ValueError(f"max_depth must be at least 3, got {max_depth}")
     depth = get_recursion_depth()
     depth = max(depth - 1, 1)  # Ignore infinite_recursion() frame.
     limit = depth + max_depth