Remove CMAKE_MODULE_PATH from critical variables list

In ros/catkin#951, `CMAKE_MODULE_PATH` was removed from the CMake
coding standards documentation "Forbidden variables" list.

This patch mirrors that change in `catkin lint`.  The variable is
removed from `critical_vars` and the corresponding tests.

Fixes fkie#55.

src/catkin_lint/checks/misc.py

@@ -78,7 +78,6 @@ def special_vars(linter):
         "CMAKE_INCLUDE_PATH",
         "CMAKE_LIBRARY_PATH",
         "CMAKE_FIND_ROOT_PATH",
-        "CMAKE_MODULE_PATH",
         "CMAKE_PREFIX_PATH"
     ])
 

test/test_checks_misc.py

@@ -39,14 +39,6 @@ def test_special_vars(self):
         self.assertEqual([ "CRITICAL_VAR_OVERWRITE" ], result)
         result = mock_lint(env, pkg, "project(mock) set(CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS} extra)", checks=cc.special_vars)
         self.assertEqual([ "CRITICAL_VAR_APPEND" ], result)
-        result = mock_lint(env, pkg, "project(mock) list(GET CMAKE_MODULE_PATH 0)", checks=cc.special_vars)
-        self.assertEqual([], result)
-        result = mock_lint(env, pkg, "project(mock) list(LENGTH CMAKE_MODULE_PATH len)", checks=cc.special_vars)
-        self.assertEqual([], result)
-        result = mock_lint(env, pkg, "project(mock) list(APPEND CMAKE_MODULE_PATH extra)", checks=cc.special_vars)
-        self.assertEqual(["CRITICAL_VAR_APPEND"], result)
-        result = mock_lint(env, pkg, "project(mock) list(REVERSE CMAKE_MODULE_PATH)", checks=cc.special_vars)
-        self.assertEqual(["CRITICAL_VAR_OVERWRITE"], result)
         result = mock_lint(env, pkg, "project(mock) list(INSERT PROJECT_NAME 0 wrong)", checks=cc.special_vars)
         self.assertEqual(["IMMUTABLE_VAR"], result)