NPM install Mongoose Kerberos error gss_acquire_cr

When I issue a npm install mongoose --save I am receiving a WARN. I am on El Capitan 10.11.1, Xcode 7.1.1 Build version 7B1005, and npm 2.14.7. Although everything is working (so far), I would like to understand this further.

Richards-MBP:app richardlu$ npm install mongoose --save
npm WARN peerDependencies The peer dependency kerberos@~0.0 included from mongodb-core will no
npm WARN peerDependencies longer be automatically installed to fulfill the peerDependency
npm WARN peerDependencies in npm 3+. Your application will need to depend on it explicitly.

> kerberos@0.0.17 install /Users/richard/okcoders/boom/app/node_modules/mongoose/node_modules/mongodb/node_modules/kerberos
> (node-gyp rebuild) || (exit 0)

  CXX(target) Release/obj.target/kerberos/lib/kerberos.o
  CXX(target) Release/obj.target/kerberos/lib/worker.o
  CC(target) Release/obj.target/kerberos/lib/kerberosgss.o
../lib/kerberosgss.c:509:13: warning: implicit declaration of function 'gss_acquire_cred_impersonate_name' is invalid in C99
      [-Wimplicit-function-declaration]
        maj_stat = gss_acquire_cred_impersonate_name(&min_stat,
                   ^
1 warning generated.
  CC(target) Release/obj.target/kerberos/lib/base64.o
  CXX(target) Release/obj.target/kerberos/lib/kerberos_context.o
  SOLINK_MODULE(target) Release/kerberos.node
mongoose@4.2.5 node_modules/mongoose
├── ms@0.7.1
├── async@0.9.0
├── hooks-fixed@1.1.0
├── regexp-clone@0.0.1
├── mpromise@0.5.4
├── mpath@0.1.1
├── muri@1.0.0
├── sliced@0.0.5
├── kareem@1.0.1
├── bson@0.4.19
├── mquery@1.6.3 (bluebird@2.9.26)
└── mongodb@2.0.48 (es6-promise@2.1.1, readable-stream@1.0.31, kerberos@0.0.17, mongodb-core@1.2.21)

For some background for others. This questions stemmed from this:

failing to install mongoose npm

^ This question is an error thrown because libgcc cannot be found.

In your situation there are two warnings. The first is this:

npm WARN peerDependencies The peer dependency kerberos@~0.0 included from mongodb-core will no
npm WARN peerDependencies longer be automatically installed to fulfill the peerDependency
npm WARN peerDependencies in npm 3+. Your application will need to depend on it explicitly.

These are NPM dependency warnings that state (in this case) that mongodb-core depends on kerberos and (maybe because kerberos offers custom functionality that is not completely necessary for mongodb-core to function), it will not be installed as an included dependency of mongodb-core in npm version 3+ in the future (and you will have to install it explicitly if you need it).

The second warning is this:

warning: implicit declaration of function 'gss_acquire_cred_impersonate_name' is invalid in C99

This means that, in the C99 standard, implicit function declarations (without supplying a header signature - read about header and implementation files) are not allowed. However, when kerberos is being built, they have supplied the -Wimplicit-function-declaration to the C compiler that tells it to throw a warning rather than error out (so they are expecting this to happen).