Gracefully handle GCS default client error

GCS default client setup can error out if dependencies is not available.
This is currently only true because b2t can be installed with only the s3 dependency.
S3 dependencies are always guranteed if s3 or cloud dependencies are installed

Author: kaitj

bids2table/_pathlib.py

@@ -1,13 +1,20 @@
 from pathlib import Path
 
 try:
-    from cloudpathlib import AnyPath, CloudPath, GSClient, S3Client
+    from cloudpathlib import AnyPath, CloudPath, S3Client
 
     _CLOUDPATHLIB_AVAILABLE = True
-
-    # Set default clients for cloud paths
     S3Client(no_sign_request=True).set_as_default_client()
-    GSClient().set_as_default_client()
+
+    # Necessary while s3 dependencies can be installed without gcs dependencies
+    try:
+        from cloudpathlib import GSClient
+
+        GSClient().set_as_default_client()
+    # Using generalized Exception here, as DefaultCredentialsError is not available for
+    # import if GSClient is not available
+    except Exception:
+        pass
 
 except ImportError:
     AnyPath = CloudPath = Path