[Test] try to build sheet with musescore on travis

[Datseris]

I have 0.0001% faith that this will work.

https://juliamusic.github.io/JuliaMusic_documentation.jl/previews/PR8/

[Datseris]

Yeap, it didn't work, but also I don't know why:

https://travis-ci.org/JuliaMusic/JuliaMusic_documentation.jl/builds/651148589#L758

┌ Error: Exception while generating log record in module Documenter.Expanders at /home/travis/.julia/packages/Documenter/HmOsT/src/Expanders.jl:564
│   exception =
│    UndefRefError: access to undefined reference
│    Stacktrace:
│     [1] getproperty at ./Base.jl:20 [inlined]
│     [2] showerror(::IOContext{Base.GenericIOBuffer{Array{UInt8,1}}}, ::SystemError) at ./errorshow.jl:118
│     [3] showvalue at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.3/Logging/src/ConsoleLogger.jl:51 [inlined]
│     [4] #handle_message#2(::Nothing, ::Base.Iterators.Pairs{Symbol,SystemError,Tuple{Symbol},NamedTuple{(:value,),Tuple{SystemError}}}, ::typeof(Base.CoreLogging.handle_message), ::Logging.ConsoleLogger, ::Base.CoreLogging.LogLevel, ::String, ::Module, ::String, ::Symbol, ::String, ::Int64) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.3/Logging/src/ConsoleLogger.jl:117
│     [5] (::Base.CoreLogging.var"#kw##handle_message")(::NamedTuple{(:value,),Tuple{SystemError}}, ::typeof(Base.CoreLogging.handle_message), ::Logging.ConsoleLogger, ::Base.CoreLogging.LogLevel, ::String, ::Module, ::String, ::Symbol, ::String, ::Int64) at ./none:0

when calling musescore(...).