add constant for read-execute permissions

Author: gilesknap

src/deploy_tools/app_builder.py

@@ -103,6 +103,8 @@ def _create_shell_file(self, app: ShellApp, module: Module) -> None:
             create_parents=True,
         )
 
+    ALL_READ_EXECUTE_PERMISSIONS = 0o555
+
     def _create_binary_file(self, app: BinaryApp, module: Module) -> None:
         """
         Download a URL, validate it against its sha256, make it executable
@@ -135,5 +137,4 @@ def _create_binary_file(self, app: BinaryApp, module: Module) -> None:
             if h.hexdigest() != app.hash:
                 raise AppBuilderError(f"Downloaded Binary {app.url} digest failure")
 
-        # TODO Martin suggests moving this
-        binary_path.chmod(0o555)
+        binary_path.chmod(self.ALL_READ_EXECUTE_PERMISSIONS)