title: Can install specific version of Tensorflow from pipenv, but cannot install it from Pipfile
body: <p>Really strange error where I can install <code>tensorflow==2.4.1</code> from pipenv using the command</p>
  <p><code>pipenv install tensorflow==2.4.1</code></p>
  <p>But when I put it in a pipfile in the format of:</p>
  <pre><code>[[source]]
  url = &quot;https://pypi.org/simple&quot;
  verify_ssl = true
  name = &quot;pypi&quot;
  
  [packages]
  tensorflow = &quot;==2.4.1&quot;
  
  [requires]
  python_version = &quot;3.8&quot;
  </code></pre>
  <p>and I run the command:</p>
  <pre><code>pipenv lock --clear
  pipenv --rm 
  pipenv install
  </code></pre>
  <p>I get:</p>
  <pre><code>Pipfile.lock (bf56f7) out of date, updating to (0575f6)...
  Locking [dev-packages] dependencies...
  Locking [packages] dependencies...
  Building requirements...
  Resolving dependencies...
  ✘ Locking Failed!
  CRITICAL:pipenv.patched.notpip._internal.index.package_finder:Could not find a version that satisfies the requirement tensorflow==2.4.1 (from -r /var/folders/m6/kqrmfdj12x79gmbbq6f2m1ph0000gn/T/pipenvxgupglu4requirements/pipenv-puyj_a_j-constraints.txt (line 2)) (from versions: none)
  [ResolutionFailure]:   File &quot;/usr/local/Cellar/pipenv/2020.11.15/libexec/lib/python3.9/site-packages/pipenv/resolver.py&quot;, line 741, in _main
  [ResolutionFailure]:       resolve_packages(pre, clear, verbose, system, write, requirements_dir, packages, dev)
  [ResolutionFailure]:   File &quot;/usr/local/Cellar/pipenv/2020.11.15/libexec/lib/python3.9/site-packages/pipenv/resolver.py&quot;, line 702, in resolve_packages
  [ResolutionFailure]:       results, resolver = resolve(
  [ResolutionFailure]:   File &quot;/usr/local/Cellar/pipenv/2020.11.15/libexec/lib/python3.9/site-packages/pipenv/resolver.py&quot;, line 684, in resolve
  [ResolutionFailure]:       return resolve_deps(
  [ResolutionFailure]:   File &quot;/usr/local/Cellar/pipenv/2020.11.15/libexec/lib/python3.9/site-packages/pipenv/utils.py&quot;, line 1395, in resolve_deps
  [ResolutionFailure]:       results, hashes, markers_lookup, resolver, skipped = actually_resolve_deps(
  [ResolutionFailure]:   File &quot;/usr/local/Cellar/pipenv/2020.11.15/libexec/lib/python3.9/site-packages/pipenv/utils.py&quot;, line 1108, in actually_resolve_deps
  [ResolutionFailure]:       resolver.resolve()
  [ResolutionFailure]:   File &quot;/usr/local/Cellar/pipenv/2020.11.15/libexec/lib/python3.9/site-packages/pipenv/utils.py&quot;, line 833, in resolve
  [ResolutionFailure]:       raise ResolutionFailure(message=str(e))
  [pipenv.exceptions.ResolutionFailure]: Warning: Your dependencies could not be resolved. You likely have a mismatch in your sub-dependencies.
    First try clearing your dependency cache with $ pipenv lock --clear, then try the original command again.
   Alternatively, you can use $ pipenv install --skip-lock to bypass this mechanism, then run $ pipenv graph to inspect the situation.
    Hint: try $ pipenv lock --pre if it is a pre-release dependency.
  ERROR: No matching distribution found for tensorflow==2.4.1 (from -r /var/folders/m6/kqrmfdj12x79gmbbq6f2m1ph0000gn/T/pipenvxgupglu4requirements/pipenv-puyj_a_j-constraints.txt (line 2))
  </code></pre>
  <p>I have committed myself to making pipenv work and am not amenable to other solutions for package management.</p>