Environment.yml without pip makes conda throw exception

[nehaljwani]

Create an environment.yml file with at least one pip package as dependency.

(root) [root@5099f186ec7f ~]# cat /tmp/batcave.yml           
name: justice_league
dependencies:
  - pip:
    - supermann==3.2.0

Now try to create an environment using this file:

(root) [root@5099f186ec7f ~]# conda env create -f /tmp/batcave.yml                                                                                                                                                 
Fetching package metadata .........
Solving package specifications: An unexpected error has occurred.

Current conda install:

               platform : linux-64
          conda version : 4.3.11
       conda is private : False
      conda-env version : 4.3.11
    conda-build version : not installed
         python version : 2.7.13.final.0
       requests version : 2.12.4
       root environment : /conda  (writable)
    default environment : /conda
       envs directories : /conda/envs
                          /root/.conda/envs
          package cache : /conda/pkgs
                          /root/.conda/pkgs
           channel URLs : https://repo.continuum.io/pkgs/free/linux-64
                          https://repo.continuum.io/pkgs/free/noarch
                          https://repo.continuum.io/pkgs/r/linux-64
                          https://repo.continuum.io/pkgs/r/noarch
                          https://repo.continuum.io/pkgs/pro/linux-64
                          https://repo.continuum.io/pkgs/pro/noarch
            config file : /root/.condarc
           offline mode : False
             user-agent : conda/4.3.11 requests/2.12.4 CPython/2.7.13 Linux/4.8.6-300.fc25.x86_64 CentOS/6.8 glibc/2.12
                UID:GID : 0:0

`$ /conda/bin/conda-env create -f /tmp/batcave.yml`

    Traceback (most recent call last):
      File "/conda/lib/python2.7/site-packages/conda/exceptions.py", line 616, in conda_exception_handler
        return_value = func(*args, **kwargs)
      File "/conda/lib/python2.7/site-packages/conda_env/cli/main_create.py", line 112, in execute
        installer.install(prefix, pkg_specs, args, env)
      File "/conda/lib/python2.7/site-packages/conda_env/installers/pip.py", line 8, in install
        pip_cmd = pip_args(prefix) + ['install', ] + specs
    TypeError: unsupported operand type(s) for +: 'NoneType' and 'list'

Delete the failed environment, add pip as a dependency and try again (which works):

(root) [root@5099f186ec7f ~]# conda env remove -yn justice_league                                                                                                                                                  

Remove all packages in environment /conda/envs/justice_league:

(root) [root@5099f186ec7f ~]# cat /tmp/batcave.yml                                                                                                                                                                 
name: justice_league
dependencies:
  - pip=9.0.1=py27_1
  - pip:
    - supermann==3.2.0
(root) [root@5099f186ec7f ~]# conda env create -f /tmp/batcave.yml                                                                                                                                                 
Fetching package metadata .........
Solving package specifications: .
openssl-1.0.2k 100% |###################################################################################################################################################################| Time: 0:00:00   3.36 MB/s
readline-6.2-2 100% |###################################################################################################################################################################| Time: 0:00:00   6.26 MB/s
sqlite-3.13.0- 100% |###################################################################################################################################################################| Time: 0:00:00   8.64 MB/s
tk-8.5.18-0.ta 100% |###################################################################################################################################################################| Time: 0:00:00  11.57 MB/s
zlib-1.2.8-3.t 100% |###################################################################################################################################################################| Time: 0:00:00  12.55 MB/s
python-2.7.13- 100% |###################################################################################################################################################################| Time: 0:00:01  11.06 MB/s
setuptools-27. 100% |###################################################################################################################################################################| Time: 0:00:00  11.93 MB/s
wheel-0.29.0-p 100% |###################################################################################################################################################################| Time: 0:00:00  15.31 MB/s
pip-9.0.1-py27 100% |###################################################################################################################################################################| Time: 0:00:00  10.68 MB/s
Collecting supermann==3.2.0
  Downloading supermann-3.2.0-py2-none-any.whl
Collecting click>=6.6 (from supermann==3.2.0)
  Downloading click-6.7-py2.py3-none-any.whl (71kB)
    100% |################################| 71kB 493kB/s 
Collecting psutil>=4.3.0 (from supermann==3.2.0)
  Downloading psutil-5.2.1.tar.gz (347kB)
    100% |################################| 348kB 679kB/s 
Collecting blinker>=1.1 (from supermann==3.2.0)
  Downloading blinker-1.4.tar.gz (111kB)
    100% |################################| 112kB 7.5MB/s 
Collecting riemann-client>=6.3.0 (from supermann==3.2.0)
  Downloading riemann_client-6.3.0-py2-none-any.whl
Collecting supervisor<4.0,>=3.0 (from supermann==3.2.0)
  Downloading supervisor-3.3.1.tar.gz (415kB)
    100% |################################| 419kB 3.5MB/s 
Collecting protobuf<4.0.0,>=2.3.0 (from riemann-client>=6.3.0->supermann==3.2.0)
  Using cached protobuf-3.2.0-cp27-cp27mu-manylinux1_x86_64.whl
Collecting meld3>=0.6.5 (from supervisor<4.0,>=3.0->supermann==3.2.0)
  Downloading meld3-1.0.2-py2.py3-none-any.whl
Collecting six>=1.9 (from protobuf<4.0.0,>=2.3.0->riemann-client>=6.3.0->supermann==3.2.0)
  Downloading six-1.10.0-py2.py3-none-any.whl

Expected:
Either throw an error stating that pip hasn't been specified as a dependency, or automatically add pip as dependency whenever any pip package has been specified in the env.yml file.

[goanpeca]

This does not seem to be an issue at the moment with 4.5.x series. Closing

[github-actions]

Hi there, thank you for your contribution to Conda!

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