Add blocked email error message to localisation files

conf/locale/locale_en-GB.ini

@@ -230,6 +230,7 @@ captcha_incorrect=Captcha didn't match.
 password_not_match=Password and confirm password are not same.
 
 username_been_taken=Username has already been taken.
+email_not_allowed=Signup failed. Please contact the site administrators.
 repo_name_been_taken=Repository name has already been taken.
 org_name_been_taken=Organisation name has already been taken.
 team_name_been_taken=Team name has already been taken.

conf/locale/locale_en-US.ini

@@ -230,6 +230,7 @@ captcha_incorrect = Captcha didn't match.
 password_not_match = Password and confirm password are not same.
 
 username_been_taken = Username has already been taken.
+email_not_allowed=Signup failed. Please contact the site administrators.
 repo_name_been_taken = Repository name has already been taken.
 org_name_been_taken = Organization name has already been taken.
 team_name_been_taken = Team name has already been taken.

routes/user/auth.go

@@ -353,7 +353,7 @@ func SignUpPost(c *context.Context, cpt *captcha.Captcha, f form.Register) {
 			c.FormErr("UserName")
 			c.RenderWithErr(c.Tr("user.form.name_pattern_not_allowed", err.(models.ErrNamePatternNotAllowed).Pattern), SIGNUP, &f)
 		case models.IsErrBlockedDomain(err):
-			c.RenderWithErr("Signup failed. Please contact the site administrators.", SIGNUP, &f)
+			c.RenderWithErr(c.Tr("form.email_not_allowed"), SIGNUP, &f)
 		default:
 			c.ServerError("CreateUser", err)
 		}