Flux - Add FluxExecutor using native Flux Python API bindings

libensemble/executors/__init__.py

@@ -1,4 +1,11 @@
 from libensemble.executors.executor import Executor
 from libensemble.executors.mpi_executor import MPIExecutor
 
-__all__ = ["Executor", "MPIExecutor"]
+# FluxExecutor is optional - requires flux-core Python bindings
+try:
+    from libensemble.executors.flux_executor import FluxExecutor  # noqa: F401
+
+    __all__ = ["Executor", "MPIExecutor", "FluxExecutor"]
+except ImportError:
+    # flux-core not available - FluxExecutor won't be importable
+    __all__ = ["Executor", "MPIExecutor"]