Exception if no sources

CONTRIBUTING.md

@@ -15,7 +15,8 @@ The process for contributions is roughly as follows:
   * If you are curious why we would require a CLA, we agree with Julien Ponge - take a look at his [post](https://julien.ponge.org/blog/in-defense-of-contributor-license-agreements/).
  * You agree to follow the [etiquette regarding communication](https://github.com/chocolatey/choco#etiquette-regarding-communication).
 
-### Definition of Trivial Contributions
+### Definition of Trivial Contributions
+
 
 It's hard to define what is a trivial contribution. Sometimes even a 1 character change can be considered significant. Unfortunately because it can be subjective, the decision on what is trivial comes from the committers of the project and not from folks contributing to the project. It is generally safe to assume that you may be subject to signing the [CLA](https://www.clahub.com/agreements/chocolatey/choco) and be prepared to do so. Ask in advance if you are not sure and for reasons are not able to sign the [CLA](https://www.clahub.com/agreements/chocolatey/choco).
 
@@ -36,7 +37,7 @@ What is generally not considered trivial:
  * Through GitHub, or through the [mailing list](https://groups.google.com/forum/#!forum/chocolatey) (preferred), you talk about a feature you would like to see (or a bug), and why it should be in Chocolatey.
    * If approved through the mailing list, ensure the accompanying GitHub issue is created with information and a link back to the mailing list discussion.
  * Once you get a nod from one of the [Chocolatey Team](https://github.com/chocolatey?tab=members), you can start on the feature.
- * Alternatively, if a feature is on the issues list with the [Up For Grabs](https://github.com/chocolatey/choco/issues?q=is%3Aopen+is%3Aissue+label%3A%22Up+For+Grabs%22) label, it is open for a community member to patch. You should comment that you are signing up for it on the issue so someone else doesn't also sign up for the work.
+ * Alternatively, if a feature is on the issues list with the [Up For Grabs](https://github.com/chocolatey/choco/issues?q=is%3Aopen+is%3Aissue+label%3A%22Up+For+Grabs%22) label, it is open for a community member (contributor) to patch. You should comment that you are signing up for it on the issue so someone else doesn't also sign up for the work.
 
 ### Set Up Your Environment
 

src/chocolatey/infrastructure.app/services/ChocolateyPackageService.cs

@@ -304,10 +304,18 @@ public ConcurrentDictionary<string, PackageResult> install_run(ChocolateyConfigu
         {
             this.Log().Info(@"Installing the following packages:");
             this.Log().Info(ChocolateyLoggers.Important, @"{0}".format_with(config.PackageNames));
-            this.Log().Info(@"By installing you accept licenses for the packages.");
 
             var packageInstalls = new ConcurrentDictionary<string, PackageResult>();
 
+            if (config.Sources == null)
+            {
+                this.Log().Error(ChocolateyLoggers.Important, @"Installation was NOT successful. There are no sources enabled for packages.");
+                Environment.ExitCode = 1;
+                return packageInstalls;
+            }
+
+            this.Log().Info(@"By installing you accept licenses for the packages.");
+
             foreach (var packageConfig in set_config_from_package_names_and_packages_config(config, packageInstalls).or_empty_list_if_null())
             {
                 Action<PackageResult> action = null;