feat(project-template): Find python modules (#44)

Add a simple cmake helper to find installed python modules. This is
mostly useful if the tests have some dependency on some python modules

cmake/Modules/FindPythonModule.cmake

+# SPDX-FileCopyrightText: Deutsches Elektronen-Synchrotron DESY, MSK, ChimeraTK Project <chimeratk-support@desy.de>
+# SPDX-License-Identifier: LGPL-3.0-or-later
+
+# cmake module for checking the existence python modules
+# Usage: find_package(PythonModule COMPONENTS module_a module_b)
+#
+# returns:
+#   PythonModule_FOUND : true if all listed components could be imported as a module
+#   PythonModule_<module>_FOUND: true if this particular module was found, false otherwise
+
+# First check for python executable if not provided
+if(NOT Python_EXECUTABLE)
+    message(STATUS "PythonModule: No python executable found, looking for python 3.0 as baseline")
+    find_package(Python 3.0 REQUIRED COMPONENTS Interpreter)
+endif()
+
+# Work-around so that we can use find_package_handle_standard_args to do the magic regarding components
+set (_PythonModule_Run "yes")
+
+message(STATUS "Checking for requested python modules, using ${Python_EXECUTABLE}")
+list(APPEND CMAKE_MESSAGE_INDENT "  ") 
+foreach(python_module ${PythonModule_FIND_COMPONENTS})
+    execute_process(
+        COMMAND ${Python_EXECUTABLE} -c "import ${python_module}"
+        ERROR_VARIABLE DUMMY
+        OUTPUT_VARIABLE DUMMY
+        RESULT_VARIABLE MODULE_RESULT)
+    if(MODULE_RESULT)
+        message("\"${python_module}\" could not be found")
+    else()
+        set(PythonModule_${python_module}_FOUND TRUE)
+        message("\"${python_module}\" seems to be available")
+    endif()
+endforeach()
+list(POP_BACK CMAKE_MESSAGE_INDENT)
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(PythonModule REQUIRED_VARS _PythonModule_Run HANDLE_COMPONENTS)