Fix bug in IRC nick collision handling.

Previously, if a bot reconnected and encountered a nick
collision, it would append '_' and connect, but counterparties
would ignore appended characters after NICK_MAX_ENCODED+2, and
so would send to the other nick. This happens in network
connection failure scenarios.
Strategy here is to simply insist on regaining the nick on that
message channel where it has been lost, retrying every 10s.
There is also a loud warning message printed.

jmdaemon/jmdaemon/irc.py

@@ -27,8 +27,12 @@ log = get_log()
 def wlog(*x):
     """Simplifier to add lists to the debug log
     """
-    msg = " ".join([str(a) for a in x])
-    log.debug(msg)
+    if x[0] == "WARNING":
+        msg = " ".join([str(a) for a in x[1:]])
+        log.warn(msg)
+    else:
+        msg = " ".join([str(a) for a in x])
+        log.debug(msg)
 
 def get_irc_text(line):
     return line[line[1:].find(':') + 2:]
@@ -310,15 +314,20 @@ class txIRC_Client(irc.IRCClient, object):
         pass
         #wlog('unhandled action: ', user, channel, msg)
 
-    def alterCollidedNick(self, nickname):
+    def irc_ERR_NICKNAMEINUSE(self, prefix, params):
         """
-        Generate an altered version of a nickname that caused a collision in an
-        effort to create an unused related name for subsequent registration.
-        :param nickname:
+        Called when we try to register or change to a nickname that is already
+        taken.
+        This is overriden from base class to insist on retrying with the same
+        nickname, after a hardcoded 10s timeout. The user is amply warned at
+        WARNING logging level, and can just restart if they are around to see it.
         """
-        newnick = nickname + '_'
-        wlog('nickname collision, changed to ', newnick)
-        return newnick
+        wlog("WARNING", "Your nickname is in use. This usually happens "
+                 "as a result of a network failure. You are recommended to "
+                 "restart, otherwise you should regain your nick after "
+                 "some time. This is not a security risk, but you may lose "
+                 "access to coinjoins during this period.")
+        reactor.callLater(10.0, self.setNick, self._attemptedNick)
 
     def modeChanged(self, user, channel, _set, modes, args):
         pass