scons: file removed from python3

Change-Id: I95794fec5cc9c6e72c9ae53f586052be71436c87
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/26249
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
diff --git a/SConstruct b/SConstruct
index 110f9c8..932eb81 100755
--- a/SConstruct
+++ b/SConstruct
@@ -1014,9 +1014,8 @@
 # value of the variable.
 def build_config_file(target, source, env):
     (variable, value) = [s.get_contents() for s in source]
-    f = file(str(target[0]), 'w')
-    print('#define', variable, value, file=f)
-    f.close()
+    with open(str(target[0]), 'w') as f:
+        print('#define', variable, value, file=f)
     return None
 
 # Combine the two functions into a scons Action object.