Merge pull request #24 from judge0/hermanzdosilovic/preview_warning_fix

Fix bug in suppressing preview warning message.

Author: hermanzdosilovic

src/judge0/__init__.py

@@ -65,9 +65,9 @@
 
 JUDGE0_IMPLICIT_CE_CLIENT = None
 JUDGE0_IMPLICIT_EXTRA_CE_CLIENT = None
-SUPPRESS_PREVIEW_WARNING = os.getenv("JUDGE0_SUPPRESS_PREVIEW_WARNING")
 
 logger = logging.getLogger(__name__)
+suppress_preview_warning = os.getenv("JUDGE0_SUPPRESS_PREVIEW_WARNING") is not None
 
 
 def _get_implicit_client(flavor: Flavor) -> Client:
@@ -107,7 +107,7 @@ def _get_implicit_client(flavor: Flavor) -> Client:
 
 
 def _get_preview_client(flavor: Flavor) -> Union[Judge0CloudCE, Judge0CloudExtraCE]:
-    if SUPPRESS_PREVIEW_WARNING is not None:
+    if not suppress_preview_warning:
         logger.warning(
             "You are using a preview version of the client which is not recommended"
             " for production.\n"