Fix bug when network map is disconnected

IPython/core/logger.py

@@ -198,7 +198,16 b' which already exists. But you must first start the logging process with'
                 odata = u'\n'.join([u'#[Out]# %s' % s
                                    for s in data.splitlines()])
                 write(u'%s\n' % odata)
-            self.logfile.flush()
+            try:
+                self.logfile.flush()
+            except OSError:
+                print("Failed to flush the log file.")
+                print(
+                    f"Please check that {self.logfname} exists and have the right permissions."
+                )
+                print(
+                    "Also consider turning off the log with `%logstop` to avoid this warning."
+                )
 
     def logstop(self):
         """Fully stop logging and close log file.