Split long lines

Use textwrap to they are split on word boundaries.  400 characters
is used as an approximation of a safe line length without dealing
with the complexity of determining the exact value for specific
conditions.  In practice, we've seen lines truncated at 435 chars.

We sleep between issuing chunks, however, we sleep less than the
normal flood protection interval so the bot still appears responsive.

Change-Id: I87d26228f0e025d911b29a1662a069a2b6d0e497

ptgbot/bot.py

@@ -24,6 +24,7 @@ import logging.config
 import os
 import time
 import ssl
+import textwrap
 
 import ptgbot.db
 
@@ -38,6 +39,11 @@ except ImportError:
 # irc-client-should-not-crash-on-failed
 # ^ This is why pep8 is a bad idea.
 irc.client.ServerConnection.buffer_class.errors = 'replace'
+# If a long message is split, how long to sleep between sending parts
+# of a message.  This is lower than the general recommended interval,
+# but in practice freenode allows short bursts at a higher rate.
+MESSAGE_CONTINUATION_SLEEP = 0.5
+# The amount of time to sleep between messages.
 ANTI_FLOOD_SLEEP = 2
 DOC_URL = 'https://git.openstack.org/cgit/openstack/ptgbot/tree/README.rst'
 
@@ -188,7 +194,14 @@ class PTGBot(irc.bot.SingleServerIRCBot):
                 return
 
     def send(self, channel, msg):
-        self.connection.privmsg(channel, msg)
+        # 400 chars is an estimate of a safe line length (which can vary)
+        chunks = textwrap.wrap(msg, 400)
+        if len(chunks) > 10:
+            raise Exception("Unusually large message: %s" % (msg,))
+        for count, chunk in enumerate(chunks):
+            self.connection.privmsg(channel, chunk)
+            if count:
+                time.sleep(MESSAGE_CONTINUATION_SLEEP)
         time.sleep(ANTI_FLOOD_SLEEP)