fix: retain os.environ obj in utils.sandboxed_env

Previously bioconda_utils.utils.sandboxed_env assigned os.environ with a
newly created dict and did not restore it to the original os.environ
object -- breaking pytest.monkeypatch.setenv (and my sanity...).

Signed-off-by: Marcel Bargull <[email protected]>

bioconda_utils/utils.py

@@ -408,19 +408,18 @@ def sandboxed_env(env):
     the existing `os.environ` or the provided **env** that match
     ENV_VAR_WHITELIST globs.
     """
+    os_environ = os.environ
+    orig = os_environ.copy()
     env = dict(env)
-    orig = os.environ.copy()
-
-    _env = {k: v for k, v in orig.items() if allowed_env_var(k)}
-    _env.update({k: str(v) for k, v in env.items() if allowed_env_var(k)})
-
-    os.environ = _env
 
     try:
+        os_environ.clear()
+        os_environ.update({k: v for k, v in orig.items() if allowed_env_var(k)})
+        os_environ.update({k: str(v) for k, v in env.items() if allowed_env_var(k)})
         yield
     finally:
-        os.environ.clear()
-        os.environ.update(orig)
+        os_environ.clear()
+        os_environ.update(orig)
 
 
 def load_all_meta(recipe, config=None, finalize=True):