`Pkg.test("PyPlot")` fails: Julia v0.6.4, system python 3.6.5, user matplotlib 2.2.3

Using Julia v0.6.4, system python 3.6.5, and user installed matplotlib 2.2.3, Pkg.test("PyPlot") fails. (PyCall and SymPy pass all self tests.)
$ ./julia --depwarn=no -e 'versioninfo();Pkg.test("PyPlot")'
Julia Version 0.6.4
Commit 9d11f62 (2018-07-09 19:09 UTC)
Platform Info:
  OS: Linux (x86_64-redhat-linux)
  CPU: Intel(R) Core(TM) i7-6700HQ CPU @ 2.60GHz
  WORD_SIZE: 64
  BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Haswell MAX_THREADS=16)
  LAPACK: libopenblas64_
  LIBM: libopenlibm
  LLVM: libLLVM-3.9.1 (ORCJIT, skylake)
INFO: Testing PyPlot
ERROR: LoadError: PyError (ccall(@pysym(:PyObject_Call), PyPtr, (PyPtr, PyPtr, PyPtr), o, pyargsptr, kw)) <class 'ValueError'>
ValueError('x and y must have same first dimension, but have shapes (1,) and (5,)',)
  File "/home/rick/.local/lib/python3.6/site-packages/matplotlib/pyplot.py", line 3363, in plot
    ret = ax.plot(*args, **kwargs)
  File "/home/rick/.local/lib/python3.6/site-packages/matplotlib/__init__.py", line 1867, in inner
    return func(ax, *args, **kwargs)
  File "/home/rick/.local/lib/python3.6/site-packages/matplotlib/axes/_axes.py", line 1528, in plot
    for line in self._get_lines(*args, **kwargs):
  File "/home/rick/.local/lib/python3.6/site-packages/matplotlib/axes/_base.py", line 406, in _grab_next_args
    for seg in self._plot_args(this, kwargs):
  File "/home/rick/.local/lib/python3.6/site-packages/matplotlib/axes/_base.py", line 383, in _plot_args
    x, y = self._xy_from_xy(x, y)
  File "/home/rick/.local/lib/python3.6/site-packages/matplotlib/axes/_base.py", line 242, in _xy_from_xy
    "have shapes {} and {}".format(x.shape, y.shape))

Stacktrace:
 [1] pyerr_check at /home/rick/.julia/v0.6/PyCall/src/exception.jl:60 [inlined]
 [2] pyerr_check at /home/rick/.julia/v0.6/PyCall/src/exception.jl:64 [inlined]
 [3] macro expansion at /home/rick/.julia/v0.6/PyCall/src/exception.jl:84 [inlined]
 [4] __pycall!(::PyCall.PyObject, ::Ptr{PyCall.PyObject_struct}, ::PyCall.PyObject, ::Ptr{Void}) at /home/rick/.julia/v0.6/PyCall/src/pyfncall.jl:101
 [5] _pycall!(::PyCall.PyObject, ::PyCall.PyObject, ::Tuple{UnitRange{Int64},UnitRange{Int64},String}, ::Int64, ::Ptr{Void}) at /home/rick/.julia/v0.6/PyCall/src/pyfncall.jl:32
 [6] _pycall!(::PyCall.PyObject, ::PyCall.PyObject, ::Tuple{UnitRange{Int64},UnitRange{Int64},String}, ::Array{Any,1}) at /home/rick/.julia/v0.6/PyCall/src/pyfncall.jl:16
 [7] #pycall#92(::Array{Any,1}, ::Function, ::PyCall.PyObject, ::Type{PyCall.PyAny}, ::UnitRange{Int64}, ::Vararg{Any,N} where N) at /home/rick/.julia/v0.6/PyCall/src/pyfncall.jl:144
 [8] pycall(::PyCall.PyObject, ::Type{PyCall.PyAny}, ::UnitRange{Int64}, ::Vararg{Any,N} where N) at /home/rick/.julia/v0.6/PyCall/src/pyfncall.jl:144
 [9] #plot#85(::Array{Any,1}, ::Function, ::UnitRange{Int64}, ::Vararg{Any,N} where N) at /home/rick/.julia/v0.6/PyPlot/src/PyPlot.jl:172
 [10] plot(::UnitRange{Int64}, ::Vararg{Any,N} where N) at /home/rick/.julia/v0.6/PyPlot/src/PyPlot.jl:169
 [11] include_from_node1(::String) at ./loading.jl:576
 [12] include(::String) at ./sysimg.jl:14
 [13] process_options(::Base.JLOptions) at ./client.jl:305
 [14] _start() at ./client.jl:371
while loading /home/rick/.julia/v0.6/PyPlot/test/runtests.jl, in expression starting on line 11
================================================================[ ERROR: PyPlot ]=================================================================

failed process: Process(`/home/rick/src/julia/julia/usr/bin/julia -Cnative -J/home/rick/src/julia/julia/usr/lib/julia/sys.so --compile=yes --depwarn=no --check-bounds=yes --code-coverage=none --color=no --compilecache=yes /home/rick/.julia/v0.6/PyPlot/test/runtests.jl`, ProcessExited(1)) [1]

==================================================================================================================================================
ERROR: PyPlot had test errors
JuliaPy / PyPlot.jl

`Pkg.test("PyPlot")` fails: Julia v0.6.4, system python 3.6.5, user matplotlib 2.2.3 #370
