phytron: fix warning on repeated comm. error

log only a warning when several retries ware successful

Change-Id: I2f1dfba920b0841914da82229820bcdd4b97c6e9

secop_psi/phytron.py

@@ -35,7 +35,9 @@ class PhytronIO(StringIO):
     identification = [('0IVR', 'MCC Minilog .*')]
 
     def communicate(self, command):
-        for ntry in range(5, 0, -1):
+        ntry = 5
+        warn = None
+        for itry in range(ntry):
             try:
                 _, _, reply = super().communicate('\x02' + command).partition('\x02')
                 if reply[0] == '\x06':  # ACK
@@ -43,9 +45,12 @@ class PhytronIO(StringIO):
                 raise CommunicationFailedError('missing ACK %r (cmd: %r)'
                                                % (reply, command))
             except Exception as e:
-                if ntry == 1:
+                if itry < ntry - 1:
+                    warn = e
+                else:
                     raise
-                self.log.warning('%s - retry', e)
+        if warn:
+            self.log.warning('needed %d retries after %r', itry, warn)
         return reply[1:]