Quote package sources that contain spaces (#943)

* Escape uris that contain spaces
cannot apply Uri.EscapeUriString blinbdly, or it will double-escape already escaped strings
For #942

* escape with ""

* Use `ArgumentEscaper.EscapeAndConcatenate` which will wrap in quotes if need be
And is generally more detailed and robust than what I  did
see https://github.com/natemcmaster/CommandLineUtils/blob/master/src/CommandLineUtils/Utilities/ArgumentEscaper.cs

Co-authored-by: Anthony Steele <anthony.steele@pockit.com>

NuKeeper.Update/Process/DotNetUpdatePackageCommand.cs

@@ -1,4 +1,6 @@
+using System;
 using System.Threading.Tasks;
+using McMaster.Extensions.CommandLineUtils;
 using NuGet.Configuration;
 using NuGet.Versioning;
 using NuKeeper.Abstractions.NuGet;
@@ -21,7 +23,7 @@ public DotNetUpdatePackageCommand(IExternalProcess externalProcess)
         {
             var projectPath = currentPackage.Path.Info.DirectoryName;
             var projectFileName = currentPackage.Path.Info.Name;
-            var sourceUrl = packageSource.SourceUri.ToString();
+            var sourceUrl = UriEscapedForArgument(packageSource.SourceUri);
             var sources = allSources.CommandLine("-s");
 
             var restoreCommand = $"restore {projectFileName} {sources}";
@@ -36,5 +38,15 @@ public DotNetUpdatePackageCommand(IExternalProcess externalProcess)
             var addCommand = $"add {projectFileName} package {currentPackage.Id} -v {newVersion} -s {sourceUrl}";
             await _externalProcess.Run(projectPath, "dotnet", addCommand, true);
         }
+
+        private static string UriEscapedForArgument(Uri uri)
+        {
+            if (uri == null)
+            {
+                return string.Empty;
+            }
+
+            return ArgumentEscaper.EscapeAndConcatenate(new string[] { uri.ToString() });
+        }
     }
 }