Plotting breaks Base.convert

[danluu]

This may be a julia bug and not a Gadfly bug, but in any case here's how to reproduce the failure. This is with Gadfly 0.3.9, julia release-0.3/e59a325* (0.3.2-pre+55). It's possible this is just another symptom of the issue in #462 , but if so, this is a stranger and more pervasive symptom.

First, run this code in the REPL

using Dates
using DataFrames
using Gadfly

a = [unix2datetime(100)]
b = [10]

df = DataFrame(x=a, y=b, label="wat")
plot(df, x=:x, y=:y, Geom.point)

then

julia> Pkg.status()
ERROR: `convert` has no method matching convert(::Type{UTF8String}, ::ASCIIString)
 in convert at base.jl:13
 in dir at pkg/git.jl:10
 in git at pkg/git.jl:16
 in success at pkg/git.jl:27
 in iscommit at pkg/git.jl:44
 in installed_version at ./pkg/read.jl:65
 in installed at ./pkg/read.jl:122
 in status at pkg/entry.jl:107
 in anonymous at pkg/dir.jl:28
 in cd at ./file.jl:20
 in cd at pkg/dir.jl:28
 in status at pkg.jl:28 (repeats 2 times)

This doesn't happen if Pkg.status() is run before plot.

[ivarne]

Looks very similar to JuliaLang/julia#8631