bokeh: Bokeh Server is incompatible with tornado=4.5

There’s a currently undiagnosed issue where Bokeh Server applications are incompatible with the newest tornado v4.5 release.

The server appears to start normally, but doesn’t receive any requests or open any sessions when queried.

To reproduce:

• Install Bokeh v0.12.5 via conda or pip
• Run a Bokeh Server app example via bokeh serve app.py (below is an example app)
• Try (and fail) to open an application session at http://localhost:5006/line_on_off in a browser or via cURL. You’ll see that any request just hangs.

contents of app.py

""" Example demonstrating turning lines on and off - with bokeh server

"""

import numpy as np

from bokeh.io import curdoc
from bokeh.layouts import row
from bokeh.palettes import Viridis3
from bokeh.plotting import figure
from bokeh.models import CheckboxGroup

p = figure()
props = dict(line_width=4, line_alpha=0.7)
x = np.linspace(0, 4 * np.pi, 100)
l0 = p.line(x, np.sin(x), color=Viridis3[0], legend="Line 0", **props)
l1 = p.line(x, 4 * np.cos(x), color=Viridis3[1], legend="Line 1", **props)
l2 = p.line(x, np.tan(x), color=Viridis3[2], legend="Line 2", **props)

checkbox = CheckboxGroup(labels=["Line 0", "Line 1", "Line 2"], active=[0, 1, 2], width=100)

def update(attr, old, new):
    l0.visible = 0 in checkbox.active
    l1.visible = 1 in checkbox.active
    l2.visible = 2 in checkbox.active

checkbox.on_change('active', update)

layout = row(checkbox, p)
curdoc().add_root(layout)

Platform: MacOS and Ubuntu 14.04 Bokeh = 0.12.5 Tornado = 4.5