skip coverage report for PRs

tools/AppVeyor.psm1

@@ -153,7 +153,7 @@ Function Invoke-CoverageReport() {
         [ValidateNotNullOrEmpty()]
         [String]$RepoToken = $Env:CoverallsToken
     )
-
+    if ( $null -ne $RepoToken) {
         Import-Module ('.\src\{0}.psm1' -f $CALLSIGN) -Verbose -Force
         $FileMap = New-PesterFileMap -SourceRoot '.\src' -PesterRoot '.\tests'
         $CoverageReport = New-CoverageReport -PesterFileMap $FileMap -RepoToken $RepoToken
@@ -161,6 +161,10 @@ Function Invoke-CoverageReport() {
         $CoverageReport | Out-String | Write-Host
         Publish-CoverageReport -CoverageReport $CoverageReport
     }
+    else {
+        Write-Warning 'CoverallsToken var given but empty. This run is triggered by a PR. Skipping coverage report...'
+    }
+}
 
 Function Invoke-AppVeyorPSGallery() {
     [CmdletBinding()]