Bug 1712819: Fix VirtualenvManager not being expandable in debugger r…

…=ahal

At least in PyCharm, expanding a `VirtualenvManager` instance means
resolving all the properties and fields of the instance.
However, if that property is doing non-trivial work, the debugger
wouldn't run that subprocess while we're stopped at a breakpoint.
So, the instance would sit there with the "Collecting data..." text.

Differential Revision: https://phabricator.services.mozilla.com/D115935

python/mach_commands.py

@@ -222,7 +222,7 @@ def run_python_tests(
         tests = mp.active_tests(
             filters=filters,
             disabled=False,
-            python=self.virtualenv_manager.version_info[0],
+            python=self.virtualenv_manager.version_info()[0],
             **mozinfo.info
         )
 

python/mozbuild/mozbuild/virtualenv.py

@@ -135,7 +135,6 @@ def virtualenv_script_path(self):
             self.topsrcdir, "third_party", "python", "virtualenv", "virtualenv.py"
         )
 
-    @property
     def version_info(self):
         return eval(
             subprocess.check_output(