Pass excludes through the stack into the call to flake8

Signed-off-by: Ryan Friedman <ryan_friedman@trimble.com>

ament_cmake_flake8/cmake/ament_cmake_flake8_lint_hook.cmake

@@ -15,5 +15,6 @@
 file(GLOB_RECURSE _python_files FOLLOW_SYMLINKS "*.py")
 if(_python_files)
   message(STATUS "Added test 'flake8' to check Python code syntax and style conventions")
-  ament_flake8()
+  message(STATUS "Configured 'flake8' exclude dirs and/or files: ${AMENT_LINT_AUTO_FILE_EXCLUDE}") 
+  ament_flake8(EXCLUDE ${AMENT_LINT_AUTO_FILE_EXCLUDE})
 endif()

ament_cmake_flake8/cmake/ament_flake8.cmake

@@ -31,13 +31,15 @@
 # :param MAX_LINE_LENGTH: override the maximum line length,
 #   the default is defined in ament_flake8
 # :type MAX_LINE_LENGTH: integer
+# :param EXCLUDE: an optional list of exclude directories or files for flake8
+# :type EXCLUDE: list
 # :param ARGN: the files or directories to check
 # :type ARGN: list of strings
 #
 # @public
 #
 function(ament_flake8)
-  cmake_parse_arguments(ARG "" "MAX_LINE_LENGTH;TESTNAME;CONFIG_FILE" "" ${ARGN})
+  cmake_parse_arguments(ARG "" "EXCLUDE;MAX_LINE_LENGTH;TESTNAME;CONFIG_FILE" "" ${ARGN})
   if(NOT ARG_TESTNAME)
     set(ARG_TESTNAME "flake8")
   endif()
@@ -57,7 +59,9 @@ function(ament_flake8)
   if(ARG_MAX_LINE_LENGTH)
     list(APPEND cmd "--linelength" "${ARG_MAX_LINE_LENGTH}")
   endif()
-  list(APPEND cmd ${ARG_UNPARSED_ARGUMENTS})
+  if(ARG_EXCLUDE)
+    list(APPEND cmd "--exclude" "${ARG_EXCLUDE}")
+  endif()
 
   file(MAKE_DIRECTORY "${CMAKE_BINARY_DIR}/ament_flake8")
   ament_add_test(