Fix bug when network map is disconnected (#13925)

Hi there :)
I encounter a little bug with the ipython logger.
When using the `%logstart` magic and writing the log to a remote path,
everything works fine until the network map gets disconnected.
After the network drive is disconnected you basically powerless, and you
have to reopen the console.

This can be easily  reproduce by sharing a windows folder

![image](https://user-images.githubusercontent.com/23289491/216761685-1bbcc92a-13e4-409c-badf-513f610fef46.png)

Mounting it using 

![image](https://user-images.githubusercontent.com/23289491/216761695-8b413c89-b4f8-4423-b9c0-d68c2997af38.png)

Start an IPython session, start a log with `%logstart Z:\log`
and disconnect.
Anything you will try to do from now on will not work, and you can't use
the Session, and will result `OSError: [Errno 22] Invalid argument`


I couldn't reproduce it in Linux environment, i guess it really depends
on the `OS` here.
Also weirdly this happens when the client close the connection. that's
mean if the Server close the connection to the mount everything still
working perfectly

I added a `try except` block to allow you to stop the logger and
continue using your ipython normally


I Search for a way to test it but I couldn't find an easy way to
reproduce it in test.

IPython/core/logger.py

@@ -1,218 +1,227 b''
 """Logger class for IPython's logging facilities.
 """
 
 #*****************************************************************************
 #       Copyright (C) 2001 Janko Hauser <[e-mail]> and
 #       Copyright (C) 2001-2006 Fernando Perez <[e-mail]>
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #*****************************************************************************
 
 #****************************************************************************
 # Modules and globals
 
 # Python standard modules
 import glob
 import io
 import os
 import time
 
 
 #****************************************************************************
 # FIXME: This class isn't a mixin anymore, but it still needs attributes from
 # ipython and does input cache management.  Finish cleanup later...
 
 class Logger(object):
     """A Logfile class with different policies for file creation"""
 
     def __init__(self, home_dir, logfname='Logger.log', loghead=u'',
                  logmode='over'):
 
         # this is the full ipython instance, we need some attributes from it
         # which won't exist until later. What a mess, clean up later...
         self.home_dir = home_dir
 
         self.logfname = logfname
         self.loghead = loghead
         self.logmode = logmode
         self.logfile = None
 
         # Whether to log raw or processed input
         self.log_raw_input = False
 
         # whether to also log output
         self.log_output = False
 
         # whether to put timestamps before each log entry
         self.timestamp = False
 
         # activity control flags
         self.log_active = False
 
     # logmode is a validated property
     def _set_mode(self,mode):
         if mode not in ['append','backup','global','over','rotate']:
             raise ValueError('invalid log mode %s given' % mode)
         self._logmode = mode
 
     def _get_mode(self):
         return self._logmode
 
     logmode = property(_get_mode,_set_mode)
 
     def logstart(self, logfname=None, loghead=None, logmode=None,
                  log_output=False, timestamp=False, log_raw_input=False):
         """Generate a new log-file with a default header.
 
         Raises RuntimeError if the log has already been started"""
 
         if self.logfile is not None:
             raise RuntimeError('Log file is already active: %s' %
                                self.logfname)
 
         # The parameters can override constructor defaults
         if logfname is not None: self.logfname = logfname
         if loghead is not None: self.loghead = loghead
         if logmode is not None: self.logmode = logmode
 
         # Parameters not part of the constructor
         self.timestamp = timestamp
         self.log_output = log_output
         self.log_raw_input = log_raw_input
 
         # init depending on the log mode requested
         isfile = os.path.isfile
         logmode = self.logmode
 
         if logmode == 'append':
             self.logfile = io.open(self.logfname, 'a', encoding='utf-8')
 
         elif logmode == 'backup':
             if isfile(self.logfname):
                 backup_logname = self.logfname+'~'
                 # Manually remove any old backup, since os.rename may fail
                 # under Windows.
                 if isfile(backup_logname):
                     os.remove(backup_logname)
                 os.rename(self.logfname,backup_logname)
             self.logfile = io.open(self.logfname, 'w', encoding='utf-8')
 
         elif logmode == 'global':
             self.logfname = os.path.join(self.home_dir,self.logfname)
             self.logfile = io.open(self.logfname, 'a', encoding='utf-8')
 
         elif logmode == 'over':
             if isfile(self.logfname):
                 os.remove(self.logfname)
             self.logfile = io.open(self.logfname,'w', encoding='utf-8')
 
         elif logmode == 'rotate':
             if isfile(self.logfname):
                 if isfile(self.logfname+'.001~'):
                     old = glob.glob(self.logfname+'.*~')
                     old.sort()
                     old.reverse()
                     for f in old:
                         root, ext = os.path.splitext(f)
                         num = int(ext[1:-1])+1
                         os.rename(f, root+'.'+repr(num).zfill(3)+'~')
                 os.rename(self.logfname, self.logfname+'.001~')
             self.logfile = io.open(self.logfname, 'w', encoding='utf-8')
 
         if logmode != 'append':
             self.logfile.write(self.loghead)
 
         self.logfile.flush()
         self.log_active = True
 
     def switch_log(self,val):
         """Switch logging on/off. val should be ONLY a boolean."""
 
         if val not in [False,True,0,1]:
             raise ValueError('Call switch_log ONLY with a boolean argument, '
                              'not with: %s' % val)
 
         label = {0:'OFF',1:'ON',False:'OFF',True:'ON'}
 
         if self.logfile is None:
             print("""
 Logging hasn't been started yet (use logstart for that).
 
 %logon/%logoff are for temporarily starting and stopping logging for a logfile
 which already exists. But you must first start the logging process with
 %logstart (optionally giving a logfile name).""")
 
         else:
             if self.log_active == val:
                 print('Logging is already',label[val])
             else:
                 print('Switching logging',label[val])
                 self.log_active = not self.log_active
                 self.log_active_out = self.log_active
 
     def logstate(self):
         """Print a status message about the logger."""
         if self.logfile is None:
             print('Logging has not been activated.')
         else:
             state = self.log_active and 'active' or 'temporarily suspended'
             print('Filename       :', self.logfname)
             print('Mode           :', self.logmode)
             print('Output logging :', self.log_output)
             print('Raw input log  :', self.log_raw_input)
             print('Timestamping   :', self.timestamp)
             print('State          :', state)
 
     def log(self, line_mod, line_ori):
         """Write the sources to a log.
 
         Inputs:
 
         - line_mod: possibly modified input, such as the transformations made
           by input prefilters or input handlers of various kinds. This should
           always be valid Python.
 
         - line_ori: unmodified input line from the user. This is not
           necessarily valid Python.
         """
 
         # Write the log line, but decide which one according to the
         # log_raw_input flag, set when the log is started.
         if self.log_raw_input:
             self.log_write(line_ori)
         else:
             self.log_write(line_mod)
 
     def log_write(self, data, kind='input'):
         """Write data to the log file, if active"""
 
         #print 'data: %r' % data # dbg
         if self.log_active and data:
             write = self.logfile.write
             if kind=='input':
                 if self.timestamp:
                     write(time.strftime('# %a, %d %b %Y %H:%M:%S\n', time.localtime()))
                 write(data)
             elif kind=='output' and self.log_output:
                 odata = u'\n'.join([u'#[Out]# %s' % s
                                    for s in data.splitlines()])
                 write(u'%s\n' % odata)
+            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.
 
         In order to start logging again, a new logstart() call needs to be
         made, possibly (though not necessarily) with a new filename, mode and
         other options."""
 
         if self.logfile is not None:
             self.logfile.close()
             self.logfile = None
         else:
             print("Logging hadn't been started.")
         self.log_active = False
 
     # For backwards compatibility, in case anyone was using this.
     close_log = logstop