Remove redundant return nil statement in user.go (#921)

Removing some redundant statements in user.go.
Adding test cases for user models.

models/models_test.go

@@ -94,12 +94,36 @@ func (s *ModelsSuite) createCampaign(ch *check.C) Campaign {
 	return c
 }
 
-func (s *ModelsSuite) TestGetUser(c *check.C) {
+func (s *ModelsSuite) TestGetUserExists(c *check.C) {
 	u, err := GetUser(1)
 	c.Assert(err, check.Equals, nil)
 	c.Assert(u.Username, check.Equals, "admin")
 }
 
+func (s *ModelsSuite) TestGetUserDoesNotExist(c *check.C) {
+	u, err := GetUser(100)
+	c.Assert(err, check.Equals, gorm.ErrRecordNotFound)
+	c.Assert(u.Username, check.Equals, "")
+}
+
+func (s *ModelsSuite) TestGetUserByAPIKeyWithExistingAPIKey(c *check.C) {
+	u, err := GetUser(1)
+	c.Assert(err, check.Equals, nil)
+
+	u, err = GetUserByAPIKey(u.ApiKey)
+	c.Assert(err, check.Equals, nil)
+	c.Assert(u.Username, check.Equals, "admin")
+}
+
+func (s *ModelsSuite) TestGetUserByAPIKeyWithNotExistingAPIKey(c *check.C) {
+	u, err := GetUser(1)
+	c.Assert(err, check.Equals, nil)
+
+	u, err = GetUserByAPIKey(u.ApiKey + "test")
+	c.Assert(err, check.Equals, gorm.ErrRecordNotFound)
+	c.Assert(u.Username, check.Equals, "")
+}
+
 func (s *ModelsSuite) TestPutUser(c *check.C) {
 	u, err := GetUser(1)
 	u.Username = "admin_changed"

models/user.go

@@ -15,10 +15,7 @@ type User struct {
 func GetUser(id int64) (User, error) {
 	u := User{}
 	err := db.Where("id=?", id).First(&u).Error
-	if err != nil {
-		return u, err
-	}
-	return u, nil
+	return u, err
 }
 
 // GetUserByAPIKey returns the user that the given API Key corresponds to. If no user is found, an
@@ -26,10 +23,7 @@ func GetUser(id int64) (User, error) {
 func GetUserByAPIKey(key string) (User, error) {
 	u := User{}
 	err := db.Where("api_key = ?", key).First(&u).Error
-	if err != nil {
-		return u, err
-	}
-	return u, nil
+	return u, err
 }
 
 // GetUserByUsername returns the user that the given username corresponds to. If no user is found, an