title: create conda env with specific python version, with that python package predownloaded
body: <p>I’m trying to create a Conda env with a specific python version, e.g.,</p>
  <pre><code>conda create --name my_env python=3.6
  </code></pre>
  <p>which gives:</p>
  <pre><code>Collecting package metadata (current_repodata.json): done
  Solving environment: done
  
  ## Package Plan ##
  
    environment location: /Users/*/anaconda3/envs/my_env
  
    added / updated specs:
      - python=3.6
  
  
  The following packages will be downloaded:
  
      package                    |            build
      ---------------------------|-----------------
      python-3.6.12              |       h26836e1_2        16.9 MB
      ------------------------------------------------------------
                                             Total:        16.9 MB
  
  The following NEW packages will be INSTALLED:
  
    ca-certificates    pkgs/main/osx-64::ca-certificates-2020.7.22-0
    certifi            pkgs/main/osx-64::certifi-2020.6.20-py36_0
    libcxx             pkgs/main/osx-64::libcxx-10.0.0-1
    libedit            pkgs/main/osx-64::libedit-3.1.20191231-h1de35cc_1
    libffi             pkgs/main/osx-64::libffi-3.3-hb1e8313_2
    ncurses            pkgs/main/osx-64::ncurses-6.2-h0a44026_1
    openssl            pkgs/main/osx-64::openssl-1.1.1g-h1de35cc_0
    pip                pkgs/main/osx-64::pip-20.2.2-py36_0
    python             pkgs/main/osx-64::python-3.6.12-h26836e1_2
    readline           pkgs/main/osx-64::readline-8.0-h1de35cc_0
    setuptools         pkgs/main/osx-64::setuptools-49.6.0-py36_0
    sqlite             pkgs/main/osx-64::sqlite-3.33.0-hffcf06c_0
    tk                 pkgs/main/osx-64::tk-8.6.10-hb0a8c7a_0
    wheel              pkgs/main/noarch::wheel-0.35.1-py_0
    xz                 pkgs/main/osx-64::xz-5.2.5-h1de35cc_0
    zlib               pkgs/main/osx-64::zlib-1.2.11-h1de35cc_3
  </code></pre>
  <p>But since I continue getting this error when it's trying to download the python package:</p>
  <pre><code>Downloading and Extracting Packages
  python-3.6.12        | 16.9 MB   | ###################################################################################6                             |  75% 
  
  CondaError: Downloaded bytes did not match Content-Length
    url: https://repo.anaconda.com/pkgs/main/osx-64/python-3.6.12-h26836e1_2.conda
    target_path: /Users/*/anaconda3/pkgs/python-3.6.12-h26836e1_2.conda
    Content-Length: 17674328
    downloaded bytes: 13207996
  </code></pre>
  <p>I decided to download the python package first via <code>curl</code>:</p>
  <pre><code>curl https://repo.anaconda.com/pkgs/main/osx-64/python-3.6.12-h26836e1_2.conda --output /Users/*/anaconda3/pkgs/python-3.6.12-h26836e1_2.conda
  </code></pre>
  <p>However, when I run the create env command again, I see that it is trying the download the package package again... Is there a way to tell conda to install from the package that I already downloaded instead of downloading it again? Thanks in advance!!!</p>