fix matplotlib headless

src/ScanPGunVgrid.py

@@ -21,9 +21,11 @@ import sys, os
 import time
 import numpy as np
 import io
-import matplotlib.pyplot as plt
-import requests
 
+import matplotlib
+import requests
+matplotlib.use('Agg')
+import matplotlib.pyplot as plt
 def fig2elog(fig, text):
 
     buf = io.BytesIO()