adjusting exception message to not rely on credentials

Octokit.Tests/Exceptions/RepositoryExistsExceptionTests.cs

@@ -0,0 +1,36 @@
+using Xunit;
+
+namespace Octokit.Tests.Exceptions
+{
+    public class RepositoryExistsExceptionTests
+    {
+        public class TheMessageProperty
+        {
+            [Fact]
+            public void WhenOwnerIsNullDoNotMentionInMessage()
+            {
+                var exception = new RepositoryExistsException(
+                    null,
+                    "some-repo",
+                    false,
+                    GitHubClient.GitHubDotComUrl,
+                    new ApiValidationException());
+
+                Assert.Equal("There is already a repository named 'some-repo' for the current account.", exception.Message);
+            }
+
+            [Fact]
+            public void WhenOwnerIsNotNullMentionInMessage()
+            {
+                var exception = new RepositoryExistsException(
+                    "some-org",
+                    "some-repo",
+                    true,
+                    GitHubClient.GitHubDotComUrl,
+                    new ApiValidationException());
+
+                Assert.Equal("There is already a repository named 'some-repo' in the organization 'some-org'.", exception.Message);
+            }
+        }
+    }
+}