解决zephyr编译时遇到的：ModuleNotFoundError: No module named ‘elftools‘问题

• 编译zephyr RTOS时，使用VM ubuntu 18.04，根据zephyr 官方的指导安装了环境，编译发现报错：

imx6@imx6-vm:~/zephyrproject/zephyr$ west build -b nucleo_h743zi samples/hello_world
[1/139] Generating include/generated/kobj-t...to-str.h, include/generated/otype-to-size.h
FAILED: zephyr/include/generated/kobj-types-enum.h zephyr/include/generated/otype-to-str.h zephyr/include/generated/otype-to-size.h /home/imx6/zephyrproject/zephyr/build/zephyr/include/generated/kobj-types-enum.h /home/imx6/zephyrproject/zephyr/build/zephyr/include/generated/otype-to-str.h /home/imx6/zephyrproject/zephyr/build/zephyr/include/generated/otype-to-size.h 
cd /home/imx6/zephyrproject/zephyr/build/zephyr && /usr/bin/python3.6 /home/imx6/zephyrproject/zephyr/scripts/gen_kobject_list.py --kobj-types-output /home/imx6/zephyrproject/zephyr/build/zephyr/include/generated/kobj-types-enum.h --kobj-otype-output /home/imx6/zephyrproject/zephyr/build/zephyr/include/generated/otype-to-str.h --kobj-size-output /home/imx6/zephyrproject/zephyr/build/zephyr/include/generated/otype-to-size.h --include /home/imx6/zephyrproject/zephyr/build/zephyr/misc/generated/struct_tags.json
Traceback (most recent call last):
  File "/home/imx6/zephyrproject/zephyr/scripts/gen_kobject_list.py", line 62, in 
    import elftools
ModuleNotFoundError: No module named 'elftools'
[2/139] Generating include/generated/driver-validation.h
FAILED: zephyr/include/generated/driver-validation.h /home/imx6/zephyrproject/zephyr/build/zephyr/include/generated/driver-validation.h 
cd /home/imx6/zephyrproject/zephyr/build/zephyr && /usr/bin/python3.6 /home/imx6/zephyrproject/zephyr/scripts/gen_kobject_list.py --validation-output /home/imx6/zephyrproject/zephyr/build/zephyr/include/generated/driver-validation.h --include /home/imx6/zephyrproject/zephyr/build/zephyr/misc/generated/struct_tags.json
Traceback (most recent call last):
  File "/home/imx6/zephyrproject/zephyr/scripts/gen_kobject_list.py", line 62, in 
    import elftools
ModuleNotFoundError: No module named 'elftools'
ninja: build stopped: subcommand failed.
FATAL ERROR: command exited with status 1: /usr/bin/cmake --build /home/imx6/zephyrproject/zephyr/build

• 主要的问题是：ModuleNotFoundError: No module named 'elftools'，python的一个模块没有找到

• 尝试重新安装一遍zephyr官方的组件包，发现问题不能解决
• 尝试使用python pip3 安装，发现elftools找不到
• 尝试搜索elftools相关的python软件包，找到解决方法：

imx6@imx6-vm:~/zephyrproject/zephyr$ pip3 install pyelftools
WARNING: pip is being invoked by an old script wrapper. This will fail in a future version of pip.
Please see https://github.com/pypa/pip/issues/5599 for advice on fixing the underlying issue.
To avoid this problem you can invoke Python with '-m pip' instead of running pip directly.
Defaulting to user installation because normal site-packages is not writeable
Collecting pyelftools
  Using cached pyelftools-0.27-py2.py3-none-any.whl (151 kB)
Installing collected packages: pyelftools
Successfully installed pyelftools-0.27

• 使用：pip3 install pyelftools 解决

imx6@imx6-vm:~/zephyrproject/zephyr$ west build -b nucleo_h743zi samples/hello_world
[132/139] linking C executable zephyr/zephyr_prebuilt.elf

[139/139] linking C executable zephyr/zephyr.elf
Memory region         Used Size  Region Size  %age Used
           FLASH:       15368 B         2 MB      0.73%
            SRAM:        4256 B       512 KB      0.81%
            DTCM:          0 GB       128 KB      0.00%
           SRAM1:          0 GB       128 KB      0.00%
           SRAM2:          0 GB       128 KB      0.00%
           SRAM3:         16 KB        32 KB     50.00%
           SRAM4:          0 GB        64 KB      0.00%
     BACKUP_SRAM:          0 GB         4 KB      0.00%
        IDT_LIST:          0 GB         2 KB      0.00%

• 发现正常编译通过