Remove ipykernel Heartbeat patch when updating to ipykernel version >5

[rahulporuri]

The ipykernel Heartbeat was been patched earlier and the patch isn't needed when we update to a new version of ipykernel > 5.x.

The patched Heartbeat is used by the IPKernelApp, which can also be removed

envisage/envisage/plugins/ipython_kernel/kernelapp.py

Lines 38 to 58 in 1eccd80

	# Methods overridden from the base class ##################################
	def init_heartbeat(self):
	"""start the heart beating
	Overridden from the base class in order to swap in our own
	Heartbeat class in place of the official one. Our Heartbeat class
	is modified to allow the heartbeat thread to be shut down cleanly.
	This override can be removed once we're on ipkernel 5.x.
	"""
	# heartbeat doesn't share context, because it mustn't be blocked
	# by the GIL, which is accessed by libzmq when freeing zero-copy
	# messages
	hb_ctx = zmq.Context()
	self.heartbeat = Heartbeat(
	hb_ctx, (self.transport, self.ip, self.hb_port),
	)
	self.hb_port = self.heartbeat.port
	self.log.debug("Heartbeat REP Channel on port: %i" % self.hb_port)
	self.heartbeat.start()

https://github.com/enthought/envisage/blob/master/envisage/plugins/ipython_kernel/heartbeat.py

[rahulporuri]

FTR

• the patch was introduced in the envisage PR Fix IPython kernel-related cleanup #188
• the upstream issue is Heartbeat._bind_socket continually retries on success ipython/ipykernel#430
• the upstream fix is Fix Heartbeat._bind_socket to return on the first successful bind. ipython/ipykernel#431, which has been available and is available in v 5.3.4 of ipykernel

[mdickinson]

Closing: IPython components have been removed from Envisage.