Fix test, improve error message

Author: aleksandr-m

src/it/feature-start-2-it/verify.bsh

@@ -3,7 +3,7 @@ import org.codehaus.plexus.util.FileUtils;
 try {
     File logFile = new File(basedir, "build.log");
     String log = FileUtils.fileRead(logFile, "UTF-8");
-    if (!log.contains("Feature name is blank.")) {
+    if (!log.contains("The name of the branch is not valid or blank.")) {
         System.out.println("feature-start build.log doesn't contain error text.");
         return false;
     }

src/main/java/com/amashchenko/maven/plugin/gitflow/GitFlowFeatureStartMojo.java

@@ -176,7 +176,7 @@ private boolean validateBranchName(String name, String pattern, boolean failOnEr
                 }
             }
         } else {
-            final String error = "The name of the branch is not valid.";
+            final String error = "The name of the branch is not valid or blank.";
             getLog().warn(error);
             valid = false;