`tns plugin add/remove` fails if there is dependency referenced as file

Steps to reproduce:

git clone https://github.com/PeterStaev/NativeScript-Drop-Down
cd NativeScript-Drop-Down/demo
tns plugin remove tns-core-modules 

Result:

npm ERR! addLocal Could not install /Users/topuzov/Git/nativescript-cli-tests/NativeScript-Drop-Down/bin/dist
npm ERR! Darwin 16.1.0
npm ERR! argv "/usr/local/Cellar/node@6/6.9.5/bin/node" "/usr/local/bin/npm" "install"
npm ERR! node v6.9.5
npm ERR! npm  v3.10.10
npm ERR! path /Users/topuzov/Git/nativescript-cli-tests/NativeScript-Drop-Down/bin/dist
npm ERR! code ENOENT
npm ERR! errno -2
npm ERR! syscall open

npm ERR! enoent ENOENT: no such file or directory, open '/Users/topuzov/Git/nativescript-cli-tests/NativeScript-Drop-Down/bin/dist'
npm ERR! enoent ENOENT: no such file or directory, open '/Users/topuzov/Git/nativescript-cli-tests/NativeScript-Drop-Down/bin/dist'
npm ERR! enoent This is most likely not a problem with npm itself
npm ERR! enoent and is related to npm not being able to find a file.
npm ERR! enoent

npm ERR! Please include the following file with any support request:
npm ERR!     /Users/topuzov/Git/nativescript-cli-tests/NativeScript-Drop-Down/demo/npm-debug.log

tns plugin add/remove fails if you have another dependency referenced with path:

"dependencies": {
  "nativescript-drop-down": "file:../bin/dist",
  "tns-core-modules": "^2.5.0"
},

Reproduce the failure in NativeScript-Drop-Down/demo using the dependency "nativescript-drop-down": "file:../bin/dist" and tns plugin remove tns-core-modules. Start by tracing how tns plugin add/remove handles file-based dependencies. Done means both commands work without the npm ENOENT error.