Merge branch 'sqlite-view-nicer-err' into 'master'

Better error message when database file isn't found

See merge request detectors/pycalibration!768

webservice/sqlite_view.py

 import argparse
+import os.path
 import sqlite3
+import sys
 
 parser = argparse.ArgumentParser(
     description='Check jobs for a given proposal & run number')
@@ -14,6 +16,9 @@ sqlite_fpath = args['sqlite_fpath']
 proposal = args['proposal'].zfill(6)
 run = args['run']
 
+if not os.path.isfile(sqlite_fpath):
+    sys.exit(f"File not found: {sqlite_fpath}")
+
 conn = sqlite3.connect(sqlite_fpath)
 
 c = conn.execute(