Fix maven path for appveyor

appveyor.yml

@@ -12,7 +12,7 @@ skip_branch_with_pr: true
 
 environment:
   JAVA_HOME: C:\Program Files (x86)\Java\jdk1.8.0
-  MAVEN_HOME: C:\Program Files\Apache\maven
+  MAVEN_HOME: C:\Program Files (x86)\Apache\Maven
 
 matrix:
   fast_finish: true
@@ -23,7 +23,6 @@ build: off
 before_test:
 - cmd: echo Running scripts before build...
 - cmd: |-
-    echo %PATH%
     PATH=C:\Program Files\PostgreSQL\9.6\bin\;C:\Program Files\MySQL\MySQL Server 5.7\bin\;%PATH%
     SET MYSQL_PWD=Password12!
     mysql -u root --password=Password12! -e "create database test_db;"

refine.bat

@@ -216,11 +216,15 @@ goto end
 
 :doMvn
 if not "%MAVEN_HOME%" == "" goto gotMvnHome
-echo You must have Apache Maven installed and the MAVEN_HOME environment variable to point to it
+echo You must have Apache Maven installed and the MAVEN_HOME environment variable to point to it.
 echo.
 echo You can download it from
 echo.
 echo   https://maven.apache.org/
+echo
+echo The environment variable MAVEN_HOME should not include the final "bin" directory, such as:
+echo
+echo   C:\Program Files (x86)\Apache\Maven
 echo.
 echo If you don't know how to set environment variables, follow the instructions at
 echo.