Provide better error message when using old version of Scanner for MSBuild

[michalb-sonar]

Repro steps

Run analysis with most recent SonarC# and a Scanner for MSBuild 2.1 or less.

Expected behavior

An error stating the scanner version is not supported and the scanner needs to be upgraded. Perhaps with a link to how to downgrade C# plugin as a workaround.

Actual behavior

Could not find a file on the SonarQube server. Url: http://sonarqubeserver/static/csharp/SonarQube.MSBuild.Runner.Implementation.zip

Failed to update the SonarQube Scanner for MSBuild binaries. Check the server url, verify that the C# plugin is correctly installed on the SonarQube server and that the SonarQube server has been restarted.

Pre-processing failed. Exit code: 1

ERROR: Execution of SonarQube Scanner for MSBuild failed (exit code 1)

Known workarounds

• Downgrade C# plugin to 5.11 (build 1761).
• Upgrade the scanner to 2.2 or superior (may not always be an option).

Related information

• SonarC# Version: 6.0+
• Scanner for MSBuild Version: 2.1 and older.