julia> Pkg.installed("Colors")
v"0.7.3"

julia> Pkg.add("Colors")
ERROR: GitError(Code:ENOTFOUND, Class:Odb, Object not found - no match for id (9f3aa6b6174c378503f612a44c0854e78c8c9a83))
macro expansion at ./libgit2/error.jl:99 [inlined]
Base.LibGit2.GitTree(::Base.LibGit2.GitRepo, ::String) at ./libgit2/repository.jl:115
#isdiff#76(::Bool, ::Function, ::Base.LibGit2.GitRepo, ::String, ::String) at ./libgit2/libgit2.jl:134
(::Base.LibGit2.#kw##isdiff)(::Array{Any,1}, ::Base.LibGit2.#isdiff, ::Base.LibGit2.GitRepo, ::String, ::String) at ./<missing>:0
isfixed(::String, ::Base.LibGit2.GitRepo, ::Dict{VersionNumber,Base.Pkg.Types.Available}) at ./pkg/read.jl:64
#7 at ./pkg/read.jl:213 [inlined]
with(::Base.Pkg.Read.##7#8{Dict{String,Tuple{VersionNumber,Bool}}}, ::Base.LibGit2.GitRepo) at ./libgit2/types.jl:597
with(::Function, ::Type{Base.LibGit2.GitRepo}, ::String, ::Vararg{String,N} where N) at ./libgit2/types.jl:603
installed(::Dict{String,Dict{VersionNumber,Base.Pkg.Types.Available}}) at ./pkg/read.jl:211
resolve at ./pkg/entry.jl:479 [inlined]
edit(::Function, ::String, ::Base.Pkg.Types.VersionSet, ::Vararg{Base.Pkg.Types.VersionSet,N} where N) at ./pkg/entry.jl:30
(::Base.Pkg.Entry.##1#3{String,Base.Pkg.Types.VersionSet})() at ./task.jl:335
Stacktrace:
 [1] sync_end() at ./task.jl:287
 [2] macro expansion at ./task.jl:303 [inlined]
 [3] add(::String, ::Base.Pkg.Types.VersionSet) at ./pkg/entry.jl:50
 [4] (::Base.Pkg.Dir.##4#7{Array{Any,1},Base.Pkg.Entry.#add,Tuple{String}})() at ./pkg/dir.jl:36
 [5] cd(::Base.Pkg.Dir.##4#7{Array{Any,1},Base.Pkg.Entry.#add,Tuple{String}}, ::String) at ./file.jl:69
 [6] #cd#1(::Array{Any,1}, ::Function, ::Function, ::String, ::Vararg{Any,N} where N) at ./pkg/dir.jl:36
 [7] add(::String) at ./pkg/pkg.jl:106