Problem in stencil generation for DerivativeOperator

[xtalax]

Upon updating one of the tests, I noticed this:

LoadError: AssertionError: Not enough points for the requested order.

  Stacktrace:
   [1] calculate_weights(::Int64, ::Float64, ::Array{Float64,1}) at /home/zander/.julia/dev/DiffEqOperators/src/derivative_operators/fornberg.jl:19
   [2] (::getfield(DiffEqOperators, Symbol("##42#44")){Float64,Int64,Array{Float64,1},Int64,Array{Float64,1},UnitRange{Int64},getfield(DiffEqOperators, Symbol("#generate_coordinates#43")){Float64}})(::Int64) at ./none:0
   [3] collect(::Base.Generator{UnitRange{Int64},getfield(DiffEqOperators, Symbol("##42#44")){Float64,Int64,Array{Float64,1},Int64,Array{Float64,1},UnitRange{Int64},getfield(DiffEqOperators, Symbol("#generate_coordinates#43")){Float64}}}) at ./generator.jl:47
   [4] DiffEqOperators.CenteredDifference{1}(::Int64, ::Int64, ::Array{Float64,1}, ::Int64, ::Nothing) at /home/zander/.julia/dev/DiffEqOperators/src/derivative_operators/derivative_operator.jl:80
   [5] DiffEqOperators.CenteredDifference{1}(::Int64, ::Int64, ::Array{Float64,1}, ::Int64) at /home/zander/.julia/dev/DiffEqOperators/src/derivative_operators/derivative_operator.jl:55
   [6] DiffEqOperators.CenteredDifference(::Int64, ::Vararg{Any,N} where N) at /home/zander/.julia/dev/DiffEqOperators/src/derivative_operators/derivative_operator.jl:166
   [7] top-level scope at /home/zander/.julia/dev/DiffEqOperators/test/generic_operator_validation.jl:14
   [8] include at ./boot.jl:326 [inlined]
   [9] include_relative(::Module, ::String) at ./loading.jl:1038
   [10] include at ./sysimg.jl:29 [inlined]
   [11] include(::String) at /home/zander/.julia/packages/SafeTestsets/A83XK/src/SafeTestsets.jl:23
   [12] top-level scope at /home/zander/.julia/dev/DiffEqOperators/test/runtests.jl:10
   [13] top-level scope at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.1/Test/src/Test.jl:1083
   [14] top-level scope at /home/zander/.julia/dev/DiffEqOperators/test/runtests.jl:10
   [15] eval(::Module, ::Any) at ./boot.jl:328
   [16] top-level scope at /home/zander/.julia/packages/SafeTestsets/A83XK/src/SafeTestsets.jl:23
   [17] top-level scope at util.jl:156
   [18] include at ./boot.jl:326 [inlined]
   [19] include_relative(::Module, ::String) at ./loading.jl:1038
   [20] include(::Module, ::String) at ./sysimg.jl:29
   [21] include(::String) at ./client.jl:403
   [22] top-level scope at none:0
   [23] eval(::Module, ::Any) at ./boot.jl:328
   [24] exec_options(::Base.JLOptions) at ./client.jl:243
   [25] _start() at ./client.jl:436
  in expression starting at /home/zander/.julia/dev/DiffEqOperators/test/generic_operator_validation.jl:12
Test Summary:                          | Error  Total
Validate and Compare Generic Operators |     1      1
ERROR: LoadError: Some tests did not pass: 0 passed, 0 failed, 1 errored, 0 broken.

Tests have been marked as broken again, this seems to imply that there is an error in generate_coordinates or in the calculation of interior_x