ParaView fails to find python3 in ubuntu

• master (13c3e2b9)
• from scratch
• up-to-date Ubuntu 18.04
• downloaded recent cmake (3.18.2 and 3.15.2)
• Python 3.6.9 from repo

~/apps/cmake-3.18.2-Linux-x86_64/bin/cmake -DPARAVIEW_USE_PYTHON=ON ../../paraview
[...]
CMake Error at /home/kitware/apps/cmake-3.18.2-Linux-x86_64/share/cmake-3.18/Modules/FindPackageHandleStandardArgs.cmake:165 (message):
  Could NOT find Python3 (missing: Python3_EXECUTABLE Interpreter) (Required
  is at least version "3.3")

      Reason given by package: 
          Interpreter: Wrong version for the interpreter "/home/kitware/.pyenv/shims/python"

Call Stack (most recent call first):
  /home/kitware/apps/cmake-3.18.2-Linux-x86_64/share/cmake-3.18/Modules/FindPackageHandleStandardArgs.cmake:458 (_FPHSA_FAILURE_MESSAGE)
  /home/kitware/apps/cmake-3.18.2-Linux-x86_64/share/cmake-3.18/Modules/FindPython/Support.cmake:2966 (find_package_handle_standard_args)
  /home/kitware/apps/cmake-3.18.2-Linux-x86_64/share/cmake-3.18/Modules/FindPython3.cmake:389 (include)
  CMakeLists.txt:461 (find_package)


-- Configuring incomplete, errors occurred!

Manually configuring with -DPython3_EXECUTABLE fixes it.