[BUG] fill_z not working for histograms

[David96]

Details

Adding fill_z to a histogram doesn't do anything for the pyplot backend, the plotly() backend crashes with ERROR: ArgumentError: Iterates of the argument to Flatten are not known to have constant length

Backends

This bug occurs on ( insert x below )

Backend	yes	no	untested
gr (default)		x
pyplot	x
plotly	x
pgfplotsx			x
unicodeplots			x
inspectdr			x
gaston			x

Versions

Plots.jl version: v1.25.8 Backend version (]st -m <backend(s)>):

• PyPlot: [d330b81b] PyPlot v2.10.0 https://github.com/JuliaPy/PyPlot.jl.git#master
• Plotly: [58dd65bb] Plotly v0.4.1

Output of versioninfo():

Julia Version 1.7.2
Commit bf53498635 (2022-02-06 15:21 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: AMD Ryzen 7 3700U with Radeon Vega Mobile Gfx
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-12.0.1 (ORCJIT, znver1)
Environment:
  JULIA_NUM_THREADS = 8

Edit: To reproduce:

data = rand(100) * 100
bin_edges = 1:10:101
color = rand(length(bin_edges) - 1)
histogram(data, fill_z=color, bins=bin_edges)