WEST ERROR: extension command build was improperly defined

[maxxlife]

I'm trying to run west, but it seems that it is quite difficult to do.
I'm trying to repeat everythin what is written here https://docs.zephyrproject.org/latest/getting_started/index.html

That error I receive when I'm running that command west build -b reel_board samples/hello_world

#############################################################
ZEPHYR_BASE=/home/maxxlife/zephyrproject/zephyr (origin: env)

ERROR: extension command build was improperly defined and could not be run: could not import /home/maxxlife/zephyrproject/zephyr/scripts/west_commands/build.py

Traceback (most recent call last):
File "/home/maxxlife/zephyrproject/.west/west/src/west/commands/command.py", line 317, in __call__
mod = _commands_module_from_file(self.py_file)
File "/home/maxxlife/zephyrproject/.west/west/src/west/commands/command.py", line 284, in _commands_module_from_file
mod = _import_mod_from(mod_name, file)
File "/home/maxxlife/zephyrproject/.west/west/src/west/commands/command.py", line 281, in _import_mod_from
spec.loader.exec_module(mod)
File "<frozen importlib._bootstrap_external>", line 678, in exec_module
File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
File "/home/maxxlife/zephyrproject/zephyr/scripts/west_commands/build.py", line 12, in <module> from cmake import DEFAULT_CMAKE_GENERATOR, run_cmake, run_build, CMakeCache ImportError: cannot import name 'DEFAULT_CMAKE_GENERATOR'`

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/home/maxxlife/zephyrproject/.west/west/src/west/main.py", line 580, in main args.handler(args, unknown)
File "/home/maxxlife/zephyrproject/.west/west/src/west/main.py", line 323, in ext_command_handler command = spec.factory()
File "/home/maxxlife/zephyrproject/.west/west/src/west/commands/command.py", line 320, in __call__
hint='could not import {}'.format(self.py_file)) from ie
west.commands.command.ExtensionCommandError
Do you know any suggestions how to solve it?

[maxxlife]

Just I need to be more careful^_^

[aeremin]

For the next poor soul who will google this error and will find this issue:
You probably missed this step:

Install needed Python packages

pip3 install --user -r ~/zephyrproject/zephyr/scripts/requirements.txt