test PyPlot failed

Windows 7 64bit
Julia 1.4.2
Python 3.8.3 `ENV["PYTHON"] = "C:\\ProgramData\\Anaconda3\\python.exe"`
Matplotlib 3.2.2

Tests passed after editing `runtests.jl`:
```
# m = match(r"%%BoundingBox: *([0-9]+) +([0-9]+) +([0-9]+) +([0-9]+)", s)
m = match(r"%%BoundingBox: *([0-9\.]+) +([0-9\.]+) +([0-9\.]+) +([0-9\.]+)", s)
```
```
# boundingbox = map(s -> parse(Int, s), m.captures)
boundingbox = map(s -> parse(Float64, s), m.captures)
```

Start in runtests.jl at the BoundingBox regular expression and parsing code, using the reported Windows 7, Julia 1.4.2, Python 3.8.3, and Matplotlib 3.2.2 setup as context. Run the PyPlot tests and verify they pass without the local edits described in the issue, including the generated bounding-box values.

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