build: check for presence of python ply

Type: improvement
Change-Id: I4f190607bfce404fbe68ec968e6923509ea9519b
Signed-off-by: Damjan Marion <dmarion@me.com>

src/tools/vppapigen/CMakeLists.txt

@@ -11,6 +11,22 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+find_package(
+  Python3
+  REQUIRED
+  COMPONENTS Interpreter
+)
+
+execute_process(
+  COMMAND ${Python3_EXECUTABLE} -c "import ply"
+  RESULT_VARIABLE _rv
+  OUTPUT_QUIET
+)
+
+if (NOT ${_rv} EQUAL 0)
+  message( FATAL_ERROR "The \"ply\" Python3 package is not installed.")
+endif()
+
 install(
   FILES vppapigen.py
   RENAME vppapigen