Q:

Yeoman can't recognize a generator that was installed globally

I ran sudo npm install -g generator-flask and it was saved.  I was able to confirm by running npm list-g.
I then run yo flask.  Thinking that this was going to work, I instead get an error message:

Error flask

You don't seem to have a generator with the name flask installed. 
You can see available generators with npm search yeoman-generator and then install them with npm install [name]. 
To see the 22 registered generators run yo with the `--help` option. 

I do as it tells me by running yo --help and discover that the flask generator is not there. 
I try this with sudo npm install -g generator-angular-flask and the problem is recreated with Angular Flask.  I'm assuming this is going to happen for all the generators which is why I've titled it as Yeoman not recognizing new npm installs. 
Does anyone know why this has happened? 

A:

A workaround, but does solve the problem:
npm link generator-angular-flask

(as does just installing the module locally)

A:

Usually it is a $NODE_PATH issue, but rather then guessing, run:
yo doctor

and follow the instructions! 

A:

Node path is the issue. 
To setup path:
export NODE_PATH=$HOME/.node/lib/node_modules/

In my case node is in HOME directory.