added save_plot documentation

doc_src/source/example_configs/reference_config.yml

@@ -44,6 +44,7 @@ config:
         investigation_time: 40.    # [optional] Duration in years; defaults
                                    # to seis_catalog duration
         annualize: True            # [optional] Annualize rates; default True
+        # save_plot: outputs/model_mfd.png  # [optional] Save the plot to this file
 
       # Maximum Magnitude Check (sanity check)
       # Checks whether the model can produce earthquakes as large as the

doc_src/source/yaml_config_file.rst

@@ -358,12 +358,22 @@ This optional section configures report generation. Currently there is one
 option, the ``basic`` HTML report, which aggregates all test and evaluation
 results into maps, plots, and tables.
 
+Report-producing tests and evaluations may include ``save_plot`` in their own
+configuration. Set it to a filename to save the generated plot; it defaults
+to ``false``.
+
 .. code-block:: yaml
 
     report:
       basic:
         outfile: outputs/report.html
 
+    config:
+      model_framework:
+        gem:
+          N_test:
+            save_plot: outputs/n_test.png
+
 
 .. _output:
 

openquake/hme/core/core.py

@@ -111,7 +111,9 @@ def read_yaml_config(
     yaml_config: Openable, fill_fields: bool = True, validate: bool = True
 ) -> dict:
     """
-    Reads a model test configuration file (YAML).
+    Reads a model test configuration file (YAML). Report-producing tests and
+    evaluations may set ``save_plot`` to a plot filename to save their plots;
+    it defaults to ``False``.
 
     :param yaml_config:
         path or file-like object in the YAML format.