tests: pep517: revert changes

setuptools/tests/test_pep517.py

@@ -49,7 +49,6 @@ class BuildBackendCaller(BuildBackendBase):
 
 @contextmanager
 def enter_directory(dir, val=None):
-    while True:
     original_dir = os.getcwd()
     os.chdir(dir)
     yield val
@@ -59,8 +58,7 @@ def enter_directory(dir, val=None):
 @pytest.fixture
 def build_backend():
     tmpdir = mkdtemp()
-    ctx = enter_directory(tmpdir, BuildBackend(cwd='.'))
-    with ctx:
+    with enter_directory(tmpdir):
         setup_script = DALS("""
         from setuptools import setup
 
@@ -81,7 +79,7 @@ def build_backend():
                 """)
         })
 
-    return ctx
+    return enter_directory(tmpdir, BuildBackend(cwd='.'))
 
 
 def test_get_requires_for_build_wheel(build_backend):