[BUG] Can't select bar_line_color in ColorBar

[marcuskd]

In Bokeh 2.1 trying to set attribute bar_line_color in the ColorBar class fails (it worked on Bokeh up to 2.0.2). Code as follows (same as User Guide -> Adding Annotations -> Colorbars with addition of setting bar_line_color)...

import numpy as np

from bokeh.models import ColorBar, LogColorMapper, LogTicker
from bokeh.plotting import figure, output_file, show

output_file('color_bar.html')

def normal2d(X, Y, sigx=1.0, sigy=1.0, mux=0.0, muy=0.0):
    z = (X-mux)**2 / sigx**2 + (Y-muy)**2 / sigy**2
    return np.exp(-z/2) / (2 * np.pi * sigx * sigy)

X, Y = np.mgrid[-3:3:100j, -2:2:100j]
Z = normal2d(X, Y, 0.1, 0.2, 1.0, 1.0) + 0.1*normal2d(X, Y, 1.0, 1.0)
image = Z * 1e6

color_mapper = LogColorMapper(palette="Viridis256", low=1, high=1e7)

plot = figure(x_range=(0,1), y_range=(0,1), toolbar_location=None)
plot.image(image=[image], color_mapper=color_mapper,
           dh=[1.0], dw=[1.0], x=[0], y=[0])

color_bar = ColorBar(color_mapper=color_mapper, ticker=LogTicker(),
                     label_standoff=12, border_line_color=None, location=(0,0),
                     bar_line_color='black')

plot.add_layout(color_bar, 'right')

show(plot)

The browser console gives the following error:

Uncaught (in promise) Error: ColorBar.bar_line_color given invalid value: {"value":"black"}
    at validate (bokeh-2.1.0.min.js:183)
    at v._update (bokeh-2.1.0.min.js:183)
    at new p (bokeh-2.1.0.min.js:183)
    at new v (bokeh-2.1.0.min.js:183)
    at new y (bokeh-2.1.0.min.js:175)
    at new l (bokeh-2.1.0.min.js:239)
    at new a (bokeh-2.1.0.min.js:233)
    at new l (bokeh-2.1.0.min.js:199)
    at new v (bokeh-2.1.0.min.js:276)
    at Function._instantiate_object (bokeh-2.1.0.min.js:162)

System:
Python 3.7.5
Bokeh 2.1.0
Chromium 81.0.4044.138
Ubuntu Mate 16.04

The same error occurred on Firefox on Ubuntu and on Chrome on Windows 10.

[mattpap]

Similar issue to #10181, but not exactly the same. The problem here is that ColorBar's visual properties in bokeh are vectoried, whereas they shouldn't be. In bokehjs they are non-vectorized and with stricter properties system, it results in this error. I will include a fix in PR #10192.

[mattpap]

Actually, it's only bar_line_* visual properties that are incorrect.

[mattpap]

We didn't catch those regressions, because defaults' tests consider v and {value: v} as interchangeable, which they aren't anymore.