text: Title: /srv/conda/envs/notebook/bin/python: No module named pip
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  ### Bug description
  
  Opening a new issue as a follow-up to the comment posted in https://github.com/jupyterhub/repo2docker/pull/1062#issuecomment-1023073794.
  
  Using the latest `repo2docker` (with `python -m pip install https://github.com/jupyterhub/repo2docker/archive/main.zip`), (existing) repos that have a custom `environment.yml` don't seem to be able to invoke `pip`, for example with `python -m pip`.
  
  #### Expected behaviour
  
  Running arbitrary `python -m pip install .` or similar should still be supported in a `postBuild` file.
  
  #### Actual behaviour
  
  Getting the following error:
  
  ```
  /srv/conda/envs/notebook/bin/python: No module named pip
  ```
  
  ### How to reproduce
  
  **With Binder**
  
  Using the test gist: https://gist.github.com/jtpio/6268417579aaf252e06c72cd3ec29ebb
  
  With `postBuild`:
  
  ```
  python -m pip --help
  ```
  
  And `environment.yml`:
  
  ```yaml
  name: test
  channels:
  - conda-forge
  dependencies:
  - python >=3.10,<3.11
  ```
  
  ![image](https://user-images.githubusercontent.com/591645/151583923-c2110d69-473a-47e3-b767-fc75b5e5e361.png)
  
  **Locally with repo2docker**
  
  ```
  mamba create -n tmp -c conda-forge python=3.10 -y
  conda activate tmp
  python -m pip install https://github.com/jupyterhub/repo2docker/archive/main.zip
  jupyter-repo2docker https://gist.github.com/jtpio/6268417579aaf252e06c72cd3ec29ebb
  ```
  
  ![image](https://user-images.githubusercontent.com/591645/151585579-60e888df-101d-4477-97f3-ef4b97c3e9c3.png)
  
  ### Your personal set up
  
  Using this gist on mybinder.org: https://gist.github.com/jtpio/6268417579aaf252e06c72cd3ec29ebb