improve partition_by missing error message

dbt/include/spark/macros/materializations/incremental/strategies.sql

@@ -77,8 +77,14 @@
     {{ get_insert_overwrite_sql(source, target, existing) }}
   {%- elif strategy == 'microbatch' -%}
     {#-- microbatch wraps insert_overwrite, and requires a partition_by config #}
+    {% set missing_partition_key_microbatch_msg -%}
+      dbt-spark 'microbatch' incremental strategy requires a `partition_by` config.
+      Ensure you are using a `partition_by` column that is of grain {{ config.get('batch_size') }}
+      for microbatch model {{ model.name }}.
+    {%- endset %}
+
     {%- if not config.get('partition_by') -%}
-      {{ exceptions.raise_compiler_error("dbt-spark 'microbatch' requires a `partition_by` config") }}
+      {{ exceptions.raise_compiler_error(missing_partition_key_microbatch_msg) }}
     {%- endif -%}
     {{ get_insert_overwrite_sql(source, target, existing) }}
   {%- elif strategy == 'merge' -%}