Problems with pythons sympy 1.7

[benneti]

Using python with sympy 1.7 results in div not being found when trying to use division on a Sym.

Error trace

this is how I stumbled over the error but one gets basically the same for Sym(2)/2. ``` julia julia> Sym(2):-one(Sym(2)):-Sym(2) ERROR: KeyError: key :__div__ not found Stacktrace: [1] __getproperty(::PyCall.PyObject, ::Symbol) at /home/benneti/.julia/packages/PyCall/BcTLp/src/PyCall.jl:307 [2] getproperty(::PyCall.PyObject, ::Symbol) at /home/benneti/.julia/packages/PyCall/BcTLp/src/PyCall.jl:312 [3] getproperty(::Sym, ::Symbol) at /home/benneti/.julia/packages/SymPy/1X20v/src/types.jl:119 [4] /(::Sym, ::Sym) at /home/benneti/.julia/packages/SymPy/1X20v/src/mathops.jl:11 [5] rem(::Sym, ::Sym) at /home/benneti/.julia/packages/SymPy/1X20v/src/generic.jl:115 [6] steprange_last(::Sym, ::Sym, ::Sym) at ./range.jl:232 [7] StepRange{Sym,Sym}(::Sym, ::Sym, ::Sym) at ./range.jl:205 [8] StepRange(::Sym, ::Sym, ::Sym) at ./range.jl:256 [9] _colon(::Sym, ::Sym, ::Sym) at ./range.jl:46 [10] (::Colon)(::Sym, ::Sym, ::Sym) at ./range.jl:40 [11] top-level scope at REPL[2]:1 ```

[jverzani]

Yes, I can do this with sympy 1.6.2:

julia> for i in Sym(2):-Sym(2):-Sym(2)
       @show i
       end
i = 2
i = 0
i = -2

julia> sympy.__version__
"1.6.2"

But I haven't tested against 1.7. I guess I need to upgrade and put out the first. Hopefully this
will have a simple workaround, but I don't know as there is nothing special done to support this syntax
on the SymPy.jl side of things.

What also gives an error, even on 1.6.2, and should be fixable, is

julia> collect(Sym(2):-Sym(2):-Sym(2))
ERROR: MethodError: no method matching Integer(::Sym)