[stable-only] Cap virtualenv for py37stable/train

py37 test started to fail with latest virtualenv (20.16.4) as it
bundles setuptools 65.3.0, which causes installation problems under
py37. (Note: with py38 the problem does not occur).

This patch sets virtualenv<20.16.4 to unblock the gate as
virtualenv 20.16.3 bundles setuptools 63.4.1, with which py37 gate
works well.

Conflicts:
  tox.ini

NOTE(elod.illes): conflict is caused by python2 dropping patch, that
  was added in ussuri: Icc43428c885853007a6ee9fc4acaf079f6349619

Change-Id: Ib68d6dc55b6d8817e52d5abdc5b2318a1fa21497
(cherry picked from commit 10410f73d636c0e3092f2ec1b1f2f0b09da94ac0)

1 files changed, 4 insertions, 0 deletions

diff --git a/tox.ini b/tox.ini
index 509eb92..48d2aed 100644
--- a/tox.ini
+++ b/tox.ini
@@ -3,6 +3,10 @@ minversion = 3.1
 envlist = py27,py37,pep8
 basepython = python3
 ignore_basepython_conflict = True
+# Pin setuptools via virtualenv as latest virtualenv pulls in 65.3.0
+# version of setuptools for py37, which causes installation problems
+# (virtualenv 20.16.3 uses setuptools 63.4.1).
+requires = virtualenv<20.16.4
 
 [testenv]
 install_command = pip install {opts} {packages}