■

Failed to use "ecto" because
  sqlite_ecto (version 1.0.2) requires ~> 1.0
  Locked to 2.0.4 in your mix.lock

とか

Failed to use "poison" (version 2.2.0) because
  ecto (version 2.0.4) requires ~> 1.5 or ~> 2.0
  phoenix (version 1.2.1) requires ~> 1.5 or ~> 2.0
  sqlite_ecto (version 1.0.2) requires ~> 1.0
  Locked to 2.2.0 in your mix.lock

とか・・・

https://github.com/hexpm/hex/issues/232

mix.exsの

  defp deps do

の中に

     {:poison, "~> 2.1", override: true},
     {:ecto, "~> 2.0", override: true},

を追加で、とりあえず、mix deps.getでのエラーは消えた。 しかし、mix ecto.gen.repo Blog.Repoすると

== Compilation error on file lib/sqlite_ecto.ex ==
** (CompileError) lib/sqlite_ecto.ex:41: no super defined for load/2 in module Sqlite.Ecto. Overridable functions available are: autogenerate/1, delete/4, dumpers/2, ensure_all_started/2, execute/6, execute_ddl/3, insert/5, insert_all/6, loaders/2, prepare/2, update/6
    lib/sqlite_ecto.ex:40: (module)

could not compile dependency :sqlite_ecto, "mix compile" failed. You can recompile this dependency with "mix deps.compile sqlite_ecto", update it with "mix deps.update sqlite_ecto" or clean it with "mix deps.clean sqlite_ecto"