nrfutil在Nixos上“导入恐怖：没有名为main的模块”

Question

我正在使用用Python实现的工具nrfutil。为了能够在NixOS下使用它，我使用了一个default.nix文件，该文件将nrfutil安装到一个venv中。这在一段时间内效果很好。（在alpine容器中使用Nix在构建服务器上的最后一次构建可以成功构建我11天前正在使用的软件。）当我执行完全相同的操作（即在不进行更改的情况下重新启动CI服务器构建）时，构建现在失败，抱怨pip不正确：

$ nix-shell 
New python executable in /home/matthias/source/tbconnect/bootloader/.venv/bin/python2.7
Not overwriting existing python script /home/matthias/source/tbconnect/bootloader/.venv/bin/python (you must use /home/matthias/source/tbconnect/bootloader/.venv/bin/python2.7)
Installing pip, wheel...
done.
Traceback (most recent call last):
  File "/home/matthias/source/tbconnect/bootloader/.venv/bin/pip", line 6, in <module>
    from pip._internal.main import main
ImportError: No module named main

在我看来，模块main应该存在：

$ ls -l .venv/lib/python2.7/site-packages/pip/_internal/main.py
-rw-r--r-- 1 matthias matthias 1359 10月 15 12:27 .venv/lib/python2.7/site-packages/pip/_internal/main.py

我不太熟悉Python环境，所以我不知道更多。有人告诉我在哪里继续调试吗？Python如何解析模块？为什么它找不到模块，它似乎呈现在我面前

这是我用来安装pip的default.nix：

with import <nixpkgs> {};
with pkgs.python27Packages;

stdenv.mkDerivation {
  name = "impurePythonEnv";
  buildInputs = [
    automake
    autoconf
    gcc-arm-embedded-7
    # these packages are required for virtualenv and pip to work:
    #
    python27Full
    python27Packages.virtualenv
    python27Packages.pip
    # the following packages are related to the dependencies of your python
    # project.
    # In this particular example the python modules listed in the
    # requirements.txt require the following packages to be installed locally
    # in order to compile any binary extensions they may require.
    #
    taglib
    openssl
    git
    stdenv
    zlib ];
  src = null;
  shellHook = ''
    # set SOURCE_DATE_EPOCH so that we can use python wheels
    SOURCE_DATE_EPOCH=$(date +%s)
    virtualenv --no-setuptools .venv
    export PATH=$PWD/.venv/bin:$PATH
    #pip install nrfutil
    pip help

    # the following is required to build micro_ecc_lib_nrf52.a in the SDK
    export GNU_INSTALL_ROOT="${gcc-arm-embedded-7}/bin/"

    unset CC
  '';
}

• 我用pip help替换了pip install nrfutil，以确保问题不是我试图安装的包本身
• 我仍然使用Python2.7，因为nrfutil仍然不适合Python3
• 无论如何，用python37替换python27并没有改变我在尝试启动pip时遇到的错误。）
• 本地使用的NixOS版本为19.09。CI docker容器中的Nix是nixos/nix:latest，它是Alpine Linux上的Nix包管理器

更新：

实际上，当我将对pip install nrfutil的调用替换为python2.7 -m pip install nrfutil时，它就工作了。这实际上让我更加困惑。python2.7正是pip的shebang中的二进制代码：

[nix-shell:~/source/tbconnect/bootloader]$ type python2.7
python2.7 is /home/matthias/source/tbconnect/bootloader/.venv/bin/python2.7

[nix-shell:~/source/tbconnect/bootloader]$ type pip
pip is /home/matthias/source/tbconnect/bootloader/.venv/bin/pip

[nix-shell:~/source/tbconnect/bootloader]$ head --lines 2 .venv/bin/pip
#!/home/matthias/source/tbconnect/bootloader/.venv/bin/python2.7
# -*- coding: utf-8 -*-

更新2: 我发现另一种解决问题的方法是编辑.venv/bin/pip。此脚本尝试了以下导入：

from pip._internal.main import main

我认为这是从PIP19.3开始的新模块路径。但我还有PIP19.2。当我将此行更改为：

from pip._internal import main

通过键入pip运行pip正在工作

问题是我不知道为什么pip脚本试图加载新的模块路径，而NixOS仍然拥有旧版本的pip

我还为NixOS在GitHub上发行了一期：https://github.com/NixOS/nixpkgs/issues/71178

Answer 1

我通过删除Python27Packages.pip使您的shell派生正常工作

(nix-shell) 2d [azul:/tmp/lixo12333] $ 
 >>> pip list
DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. A future version of pip will drop support for Python 2.7. More details about Python 2 support in pip, can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support
Package          Version
            -
behave           1.2.6  
Click            7.0    
crcmod           1.7    
ecdsa            0.13.3 
enum34           1.1.6  
future           0.18.2 
intelhex         2.2.1  
ipaddress        1.0.23 
libusb1          1.7.1  
linecache2       1.0.0  
nrfutil          5.2.0  
parse            1.12.1 
parse-type       0.5.2  
pc-ble-driver-py 0.11.4 
piccata          1.0.1  
pip              19.3.1 
protobuf         3.10.0 
pyserial         3.4    
pyspinel         1.0.0a3
PyYAML           4.2b4  
setuptools       41.6.0 
six              1.12.0 
tqdm             4.37.0 
traceback2       1.4.0  
virtualenv       16.4.3 
wheel            0.33.6 
wrapt            1.11.2 
(nix-shell) 2d [azul:/tmp/lixo12333] $ 

还有我的默认.nix

with import <nixpkgs> {};
with pkgs.python27Packages;

stdenv.mkDerivation {
  name = "impurePythonEnv";
  buildInputs = [
    automake
    autoconf
    gcc-arm-embedded-7
    # these packages are required for virtualenv and pip to work:
    #
    python27Full
    python27Packages.virtualenv
    # the following packages are related to the dependencies of your python
    # project.
    # In this particular example the python modules listed in the
    # requirements.txt require the following packages to be installed locally
    # in order to compile any binary extensions they may require.
    #
    taglib
    openssl
    git
    stdenv
    zlib ];
  src = null;
  shellHook = ''
    # set SOURCE_DATE_EPOCH so that we can use python wheels
    SOURCE_DATE_EPOCH=$(date +%s)
    virtualenv .venv
    export PATH=$PWD/.venv/bin:$PATH
    pip install nrfutil
    #pip help

    # the following is required to build micro_ecc_lib_nrf52.a in the SDK
    export GNU_INSTALL_ROOT="${gcc-arm-embedded-7}/bin/"

    unset CC
  '';
}