db_connection_migration.js

function login (email, password, callback) {

  //1. Auth user. 
  
  var profile = {
    user_id:     "103547991597142817347",
    nickname:    "johnfoo",
    email:       email,
    name:        "John Foo",
    given_name:  "John",
    family_name: "Foo"
  };
  
  //2. Auth is successful, create a user in Auth0
  createAuth0UserIfNew(profile,password,function(e){
    if(e) return callback(e);
    return callback(null, profile);
  });
  
  function createAuth0UserIfNew(user,password,done){
    getAuth0ApiToken(function(e,tok){
      if(e) return done(e);
      
      var token = tok.access_token;
      
      console.log('Got token' + token);
      
      userExists(user,'MyUsers',token,function(e,result){
        if(e) return done(e);
        if( result ) {
          console.log('User exists'); 
          return done();
        }
        console.log('User doesn\'t exist');
        
        createUser(user,password,'MyUsers',token,function(e){
          if(e) done(e);
          return done();
        });
      });
    });
  }
  
  function createUser(user,password, connection,token,done){
    
    request({
      uri: 'https://eugeniopace.auth0.com/api/users',
      method: 'POST',
      json: {
        email: user.email,
        password: password,
        connection: connection,
        email_verfied: false,
        //Other properties
      }
    },
    function(e,r,b){
      if(e) return done(e);
    
      if(r.statusCode !== 200 ) return done(new Error("Create User - Invalid response" + r.statusCode));
      return done();
    });
    
  }

  function userExists(user,connection,token,done){
      
      request({
        uri: 'https://eugeniopace.auth0.com/api/connections/'+ connection +'/users',
        qs: {
          search: 'email=' + user.email,
          per_page: 1
        },
        headers: {
          Authorization: 'Bearer ' + token
        }
      },
      function(e,r,b){
        if(e) return done(e);
        var list = JSON.parse(b);
        console.log('Users in connection');
        console.log(list);
        console.log(list.length);
        console.log(typeof(list));
        console.log(list.length);
        if(list.length > 0 ) return done(null, true);
        return done(null, false);
      });
  }
              
  function getAuth0ApiToken(done){
    request({
      uri: 'https://eugeniopace.auth0.com/oauth/token',
      method: 'POST',
      json: {
        "client_id":        "F2IEucRJQ...7ZZ0byR8lR9",
        "client_secret":    "ZotF9ylurI1xZ_cQvlGfMUC...YOp3N6Chvz_KV9BY0jgQ_1mA",
        "grant_type":       "client_credentials"
      }
    },
    function(e,r,b){
      if(e) return done(e);
    
      if(r.statusCode !== 200 ) return done(new Error("Invalid response" + r.statusCode));
    
      done(null, b);
      
    });
  }
}

Need to add . . .

,
headers: {
          Authorization: 'Bearer ' + token
}

. . . to request in createUser (before or after the json block). Otherwise that request will always fail.