Use pip==20.2.4 in tox venv

pip 20.3 is disruptive and would lead to big changes in stable
branches.

Change-Id: Ic3770f4098c52b0d26bc62291c9e79e8ee81d107
Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/tox.ini b/tox.ini
index 8532aa5e..f4df0a90 100644
--- a/tox.ini
+++ b/tox.ini
@@ -2,6 +2,7 @@
 envlist = pep8,pylint,yamllint,ansiblelint,bashate,py38,bandit,perm
 
 [testenv]
+pip_version = pip==20.2.4
 usedevelop = True
 deps =
   -chttps://git.opnfv.org/functest/plain/upper-constraints.txt