aggr.py: added more helpful exception when cluster file template missing

mossutils/aggr.py

@@ -9,12 +9,14 @@ DEFAULT_CLUSTER_FILES_DIR="_clusters"
 DEFAULT_CLUSTERS_MATCHES_CSV_FILE="clusters-matches.csv"
 DEFAULT_CLUSTER_STUDENTS_CSV_FILE_PATTERN="cluster-students-{}.csv"
 DEFAULT_CX_COURSE_STUDENTS_CSV_FILE="cx_students.csv"
+DEFAULT_JINJA_CLUSTER_TEMPLATE_FILE="./_static/clusters.html.jinja"
 
 def main(
     cluster_files_dir=DEFAULT_CLUSTER_FILES_DIR,
     clusters_matches_csv_file=DEFAULT_CLUSTERS_MATCHES_CSV_FILE,
     cluster_students_csv_file_pattern=DEFAULT_CLUSTER_STUDENTS_CSV_FILE_PATTERN,
-    cx_course_students_csv_file=DEFAULT_CX_COURSE_STUDENTS_CSV_FILE):
+    cx_course_students_csv_file=DEFAULT_CX_COURSE_STUDENTS_CSV_FILE,
+    jinja_cluster_template_file=DEFAULT_JINJA_CLUSTER_TEMPLATE_FILE):
 
   logutils.configure_level_and_format()
 
@@ -82,7 +84,11 @@ def main(
 
   jinja2_file_loader = jinja2.FileSystemLoader(".")
   jinja2_env = jinja2.Environment(loader=jinja2_file_loader)
-  template = jinja2_env.get_template("./_static/clusters.html.jinja")
+
+  try:
+    template = jinja2_env.get_template(jinja_cluster_template_file)
+  except jinja2.exceptions.TemplateNotFound as exception:
+    raise RuntimeError("Couldn't load Jinja2 template {}. Should have been created by mu-init.".format(jinja_cluster_template_file))   
 
   # output = template.render(colors=colors)
   # print(output)