Merge pull request #157 from romanbalayan/feat/docs-customScanner-sam…

…ple-usage

Modify README for customScanner sample usage.

README.md

@@ -87,8 +87,18 @@ sonar-scanner
 #### *I constantly get "Impossible to download and extract binary [...] In such situation, the best solution is to install the standard SonarScanner", what can I do?*
 
 You can install manually the [standard SonarScanner](https://redirect.sonarsource.com/doc/install-configure-scanner.html),
-which requires to have a Java Runtime Environment available too (Java 8+). Once this is done, you can replace the 2nd line
-of the example by:
+which requires to have a Java Runtime Environment available too (Java 8+). 
+
+It is important to make sure that the SonarScanner `$install_directory/bin` location is added to the system `$PATH` environment variable. This will ensure that `sonar-scanner` command will be resolved by the customScanner, and prevent the error:
+
+``` javascript
+Error: Local install of SonarScanner not found.
+    at getLocalSonarScannerExecutable (<project_dir>/node_modules/sonarqube-scanner/src/sonar-scanner-executable.js:153:11)
+    at scanUsingCustomScanner (<project_dir>/node_modules/sonarqube-scanner/src/index.js:52:3)
+...
+```    
+
+Once local installation is done, you can replace the 2nd line of the example:
 
 ```javascript
 var scanner = require('sonarqube-scanner').customScanner;