stdlib: Fix 'set_{text/json}_stats_output' in Simulator

These functions were using "os.is_path_exists_or_creatable". This is a
non-existant function. It has been replaced with a simple test to ensure
the specified stats file either exists or is creatable.

Change-Id: I9a1b2c575d18356fdc87c8b1848c09735e0f18e7
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/62971
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>

src/python/gem5/simulate/simulator.py

@@ -210,9 +210,19 @@ class Simulator:
 
         :param path: That path in which the file should be output to.
         """
-        if not os.is_path_exists_or_creatable(path):
+        path_path = Path(path)
+        parent = path_path.parent
+
+        if (
+            not parent.is_dir()
+            or not os.access(parent, os.W_OK)
+            or (
+                path_path.exists()
+                and (path_path.is_dir() or not os.access(path_path, os.W_OK))
+            )
+        ):
             raise Exception(
-                f"Path '{path}' is is not a valid text stats output location."
+                f"Specified text stats output path '{path}' is invalid."
             )
         addStatVisitor(path)
 
@@ -224,9 +234,19 @@ class Simulator:
 
         :param path: That path in which the JSON should be output to.
         """
-        if not os.is_path_exists_or_creatable(path):
+        path_path = Path(path)
+        parent = path_path.parent
+
+        if (
+            not parent.is_dir()
+            or not os.access(parent, os.W_OK)
+            or (
+                path_path.exists()
+                and (path_path.is_dir() or not os.access(path_path, os.W_OK))
+            )
+        ):
             raise Exception(
-                f"Path '{path}' is is not a valid JSON output location."
+                f"Specified json stats output path '{path}' is invalid."
             )
         addStatVisitor(f"json://{path}")