[test][prefix] Correcly silence warnings

beat/core/test/prefix/algorithms/user/shell_exec/1.py

@@ -45,6 +45,6 @@ class Algorithm:
 
     def process(self, inputs, output):
         if self.status is None:  # executes it only once
-            self.status = os.system(self.cmd)
+            self.status = os.system(self.cmd)  # nosec
             output.write({"status": numpy.int32(self.status)})
         return True

beat/core/test/prefix/plotters/user/scatter/1.py

@@ -41,7 +41,7 @@ import itertools
 # Make sure we won't require an X11 connection
 import matplotlib
 
-matplotlib.use("Agg")
+matplotlib.use("Agg")  # noqa need to happen before further imports
 
 from matplotlib.figure import Figure
 import matplotlib.pyplot as pyplot