the code written as is, is broken, as in yes i couldn't get DifferntialEquations to install, because somewhere in the dependency graph some package pins/pulls SymEngine v0.4.3 which has a deprecated use of is_windows, which is fixed in the PR that i linked to
the obvious fix was to update to the latest version of SymEngine using the #master modifier with Pkg.add() but it didn't work - it kept ignoring #master and adding v0.4.3 nonetheless. i then tried #5dfc78a, the hash of master, and neither did that work.
This is a known `Pkg` bug (the patch should be merged this week). In the meantime, you have to `pkg> rm SymEngine` followed by `pkg> add SymEngine#master`.
https://github.com/symengine/SymEngine.jl/pull/150/files
the obvious fix was to update to the latest version of SymEngine using the #master modifier with Pkg.add() but it didn't work - it kept ignoring #master and adding v0.4.3 nonetheless. i then tried #5dfc78a, the hash of master, and neither did that work.