Auto merge of #2227 - tbu-:pr_pycache, r=alexcrichton
Auto merge of #2227 - tbu-:pr_pycache, r=alexcrichton

Running `make` creates the `src/etc/__pycache__` directory which should
not be checked in.

durka/cargo,gchp/cargo,sbeckeriv/cargo,tshepang/cargo,vojtechkral/cargo,rust-lang/cargo,eminence/cargo,rustyhorde/cargo,blaenk/cargo,brson/cargo,vojtechkral/cargo,blaenk/cargo,cmr/cargo,sbeckeriv/cargo,tsurai/cargo,nipunn1313/cargo,ThinTim/cargo,rust-lang/cargo,mark-buer/cargo,AndiDog/cargo,rust-lang/cargo,rustyhorde/cargo,tshepang/cargo,tsurai/cargo,cmr/cargo,durka/cargo,durka/cargo,achanda/cargo,rustyhorde/cargo,gchp/cargo,sbeckeriv/cargo,AndiDog/cargo,vojtechkral/cargo,nipunn1313/cargo,achanda/cargo,eminence/cargo,rust-lang/cargo,AndiDog/cargo,ThinTim/cargo,brson/cargo,mark-buer/cargo,cmr/cargo,brson/cargo,eminence/cargo,nipunn1313/cargo,tshepang/cargo,eminence/cargo,tsurai/cargo,blaenk/cargo,brson/cargo,cmr/cargo,vojtechkral/cargo,tsurai/cargo,cmr/cargo,sbeckeriv/cargo,AndiDog/cargo,mark-buer/cargo,AndiDog/cargo,ThinTim/cargo,blaenk/cargo,achanda/cargo,gchp/cargo,tsurai/cargo,mark-buer/cargo,achanda/cargo,tshepang/cargo,blaenk/cargo,gchp/cargo,gchp/cargo,brson/cargo,durka/cargo,nipunn1313/cargo,ThinTim/cargo,ThinTim/cargo,mark-buer/cargo,rustyhorde/cargo