Build pep8 only when testing is enabled

Testing should be enabled for all developers and pep8
is a developers tool.

Author: aashish24

CMake/cdat_modules/pep8_pkg.cmake

@@ -11,8 +11,6 @@ string(TOUPPER ${nm} uc_nm)
 set(${uc_nm}_VERSION ${${nm}_MAJOR}.${${nm}_MINOR}.${${nm}_PATCH})
 set(PEP8_SOURCE ${PEP8_URL}/${PEP8_GZ})
 
-if (CDAT_BUILD_ALL)
+if (BUILD_TESTING)
   add_cdat_package(pep8 "" "" ON)
-else()
-  add_cdat_package(pep8 "" "" OFF)
 endif()