"No matching distribution" due to wheel tags not matching in pip 20.0

**Environment**



* pip version: 20.0.1

* Python version: 3.6.9

* OS: Ubuntu 18.04



<!-- Feel free to add more information about your environment here -->



**Description**

Pip can seemingly no longer install any version of `mxnet` newer than 0.9.5.



**Expected behavior**

It should be able to. :-) This worked before pip 20.



**How to Reproduce**

Try to install `mxnet==1.3.1` in a virtual environment.



**Output**



```

$ virtualenv -ppython3 /tmp/venv

Already using interpreter /usr/bin/python3

Using base prefix '/usr'

New python executable in /tmp/venv/bin/python3

Also creating executable in /tmp/venv/bin/python

Installing setuptools, pkg_resources, pip, wheel...done.

$ /tmp/venv/bin/pip install mxnet==1.3.1

ERROR: Could not find a version that satisfies the requirement mxnet==1.3.1 (from versions: 0.9.5)

ERROR: No matching distribution found for mxnet==1.3.1

```



Running `pip install` with `--verbose` produces a huge log, in which this seems relevant:



```

  Skipping link: none of the wheel's tags match: py2-none-manylinux1_x86_64, py3-none-manylinux1_x86_64: https://files.pythonhosted.org/packages/f0/2e/b26eb7273aed1945f59993b3b306442eb41684f931b5380821c39cf50a31/mxnet-1.3.1-py2.py3-none-manylinux1_x86_64.whl#sha256=939575fddd45e8ba39177dd3d53ccce64dea312bc08f493392b1ecace9e1b117 (from https://pypi.org/simple/mxnet/)

```

[
  {
    "category": "misspecification",
    "rule": "signature.unresolvable_declared_requirement",
    "source": "failure_signature",
    "excerpt": "ERROR: Could not find a version that satisfies the requirement mxnet==1.3.1 (from versions: 0.9.5)"
  }
]