only install enum34 python dependency if we are not using pyinstaller (#57)

Author: mlangkabel

appveyor.yml

@@ -34,7 +34,7 @@ install:
     - SET PIP_PATH=%PYTHON_PATH%/Scripts
     - SET PATH=%PYTHON_PATH%;%PIP_PATH%;%PATH%
     # install python dependencies
-    - cmd: pip install enum34
+    - cmd: IF %DEPLOY% EQU 0 pip install enum34
     - cmd: pip install parso==0.5.1
     - cmd: pip install jedi==0.15.0
     - cmd: pip install pyinstaller==%PYINSTALLER_VERSION%