Fix string slice.

Author: ionelmc

{{cookiecutter.repo_name}}/appveyor.yml

@@ -60,7 +60,7 @@ test_script:
   - '%WITH_COMPILER% %PYTHON_HOME%\Scripts\tox'
 {% if cookiecutter.c_extension_support|lower == 'yes' %}
 after_test:
-  - IF "%TOXENV:~-8,8%" == "-nocov" %WITH_COMPILER% %TOXPYTHON% setup.py bdist_wheel
+  - IF "%TOXENV:~-6,6%" == "-nocov" %WITH_COMPILER% %TOXPYTHON% setup.py bdist_wheel
 {% endif %}
 on_failure:
   - ps: dir "env:"