Added comment

Author: jaaufauvre

.travis.yml

@@ -9,6 +9,7 @@ matrix:
   - dotnet: 2.1  # latest available release
     mono: none  
     env: 
+      # Do not run analysis on PR (secure env variables like SONAR_TOKEN are not always available)
       - WITH_SONAR_ANALYSIS=$([ "$TRAVIS_PULL_REQUEST" = "false" ] && echo true || echo false)
       - TEST_RESULTS_PATH=./Mastercard.Developer.OAuth1Signer.Tests/bin
 solution: Mastercard.Developer.OAuth1Signer.sln