fix close(::Figure) and add test (#23)

Author: IanButterworth

.gitignore

@@ -0,0 +1,2 @@
+Manifest.toml
+.CondaPkg

src/PythonPlot.jl

@@ -190,7 +190,7 @@ Base.close(f::Figure) = plotclose(f)
 
 # rename to avoid type piracy:
 @doc LazyHelp(pyplot,"close") plotclose() = pyplot.close()
-plotclose(f::Figure) = pyconvert(Int, plotclose(pyconvert(Int, f.number)))
+plotclose(f::Figure) = pyconvert(Union{Nothing,Int}, plotclose(pyconvert(Int, f.number)))
 function plotclose(f::Integer)
     pop!(withfig_fignums, f, f)
     pyplot.close(f)

test/runtests.jl

@@ -37,4 +37,9 @@ rgba = PyArray(pycall(PythonPlot.ScalarMappable; cmap=c, norm=PythonPlot.Normali
                 0.8991926182237601  0.5144175317185697   0.4079200307574009   1.0
                 0.9657054978854287  0.9672433679354094   0.9680891964628989   1.0
                 0.4085351787773935  0.6687427912341408   0.8145328719723184   1.0
-                0.0196078431372549  0.18823529411764706  0.3803921568627451   1.0 ]
+                0.0196078431372549  0.18823529411764706  0.3803921568627451   1.0 ]
+
+@testset "close figure: issue 22" begin
+    f = figure()
+    @test close(f) === nothing
+end