Make BuildEnvironment._temp_dir a local variable

Author: chrahunt

src/pip/_internal/build_env.py

@@ -55,12 +55,12 @@ class BuildEnvironment(object):
 
     def __init__(self):
         # type: () -> None
-        self._temp_dir = TempDirectory(
+        temp_dir = TempDirectory(
             kind=build_env_kind, globally_managed=True
         )
 
         self._prefixes = OrderedDict((
-            (name, _Prefix(os.path.join(self._temp_dir.path, name)))
+            (name, _Prefix(os.path.join(temp_dir.path, name)))
             for name in ('normal', 'overlay')
         ))
 
@@ -79,7 +79,7 @@ def __init__(self):
                 get_python_lib(plat_specific=True),
             )
         }
-        self._site_dir = os.path.join(self._temp_dir.path, 'site')
+        self._site_dir = os.path.join(temp_dir.path, 'site')
         if not os.path.exists(self._site_dir):
             os.mkdir(self._site_dir)
         with open(os.path.join(self._site_dir, 'sitecustomize.py'), 'w') as fp: