Fix Google Dataflow hook failing import when apache-beam not installed (#65659)

Author: shahar1

providers/google/src/airflow/providers/google/cloud/hooks/dataflow.py

@@ -50,8 +50,20 @@
 from googleapiclient.discovery import Resource, build
 
 from airflow.exceptions import AirflowProviderDeprecationWarning
-from airflow.providers.apache.beam.hooks.beam import BeamHook, BeamRunnerType, beam_options_to_args
-from airflow.providers.common.compat.sdk import AirflowException, timeout
+from airflow.providers.common.compat.sdk import (
+    AirflowException,
+    AirflowOptionalProviderFeatureException,
+    timeout,
+)
+
+try:
+    from airflow.providers.apache.beam.hooks.beam import BeamHook, BeamRunnerType, beam_options_to_args
+except ImportError as e:
+    raise AirflowOptionalProviderFeatureException(
+        "Failed to import apache-airflow-providers-apache-beam. "
+        "To use the Dataflow service with Apache Beam pipelines, please install the apache-beam provider: "
+        "pip install apache-airflow-providers-apache-beam"
+    ) from e
 from airflow.providers.google.common.hooks.base_google import (
     PROVIDE_PROJECT_ID,
     GoogleBaseAsyncHook,