2.7.0 sdist is unusable (builds version "0.0.0")

[mgorny]

$ pip install --no-binary :all: testtools==2.7.0
Collecting testtools==2.7.0
  Using cached testtools-2.7.0.tar.gz (201 kB)
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
  Installing backend dependencies ... done
  Preparing metadata (pyproject.toml) ... done
  WARNING: Requested testtools==2.7.0 from https://files.pythonhosted.org/packages/06/86/5f50ae3fbcd5035a15919854b2b6c6170628693dfd4e042064273c1f6d1a/testtools-2.7.0.tar.gz, but installing version 0.0.0
Discarding https://files.pythonhosted.org/packages/06/86/5f50ae3fbcd5035a15919854b2b6c6170628693dfd4e042064273c1f6d1a/testtools-2.7.0.tar.gz (from https://pypi.org/simple/testtools/) (requires-python:>=3.7): Requested testtools==2.7.0 from https://files.pythonhosted.org/packages/06/86/5f50ae3fbcd5035a15919854b2b6c6170628693dfd4e042064273c1f6d1a/testtools-2.7.0.tar.gz has inconsistent version: expected '2.7.0', but metadata has '0.0.0'
ERROR: Could not find a version that satisfies the requirement testtools==2.7.0 (from versions: 0.9.9, 0.9.10, 0.9.11, 0.9.12, 0.9.13, 0.9.14, 0.9.15, 0.9.16, 0.9.17, 0.9.18, 0.9.19, 0.9.20, 0.9.21, 0.9.22, 0.9.23, 0.9.24, 0.9.25, 0.9.26, 0.9.27, 0.9.28, 0.9.29, 0.9.30, 0.9.32, 0.9.33, 0.9.34, 0.9.35, 0.9.36, 0.9.37, 0.9.38, 0.9.39, 1.0.0, 1.1.0, 1.2.0, 1.2.1, 1.3.0, 1.4.0, 1.5.0, 1.6.0, 1.6.1, 1.7.0, 1.7.1, 1.8.0, 1.8.1, 1.9.0, 2.0.0, 2.1.0, 2.2.0, 2.3.0, 2.4.0, 2.5.0, 2.6.0, 2.7.0)
ERROR: No matching distribution found for testtools==2.7.0