[!556] [backport] Merge branch 'bugfix/install_variable' into 'master'

Merge branch 'cherry-pick-317d5564-2' into 'releases/2.6'

fixed typo in variable

See merge request [!456]

(cherry picked from commit 317d5564)

444bac38 fixed typo in variable

See merge request [!556]

  [!456]: gitlab.dune-project.org/core/dune-common/merge_requests/456
  [!556]: gitlab.dune-project.org/core/dune-common/merge_requests/556

cmake/modules/DunePythonFindPackage.cmake

@@ -101,7 +101,7 @@ function(dune_python_find_package)
   else()
     set(${PYPACKAGE_RESULT} FALSE)
     if(PYPACKAGE_REQUIRED)
-      message(FATAL_ERROR "The python package ${PYCHECK_PACKAGE} could not be found! (for interpreter ${PYPACKAGE_INTERPRETER})")
+      message(FATAL_ERROR "The python package ${PYPACKAGE_PACKAGE} could not be found! (for interpreter ${PYPACKAGE_INTERPRETER})")
     endif()
   endif()