[tests] Don't use cffi 1.15 with Python 3.5

Bug: T293440
Change-Id: I4bd1f4c48f7ea78a2ffcc1b2f8fa02b4cae9e9f6
---
M dev-requirements.txt
1 file changed, 4 insertions(+), 0 deletions(-)

diff --git a/dev-requirements.txt b/dev-requirements.txt
index 7e0cdbc..8dbd64c 100644
--- a/dev-requirements.txt
+++ b/dev-requirements.txt
@@ -11,6 +11,10 @@
 # Python 3.8 needs werkzeug >= 0.15.5
 # GitHub vulnerable dependency suggests werkzeug >= 0.15.3
 werkzeug>=0.15.5
+
+# T293440: pytest-httpbin needs cffi >=1.0.0
+# but Python 3.5 needs cffi < 1.15 which is not taken into account
+cffi >= 1.0.0, < 1.15.0 ;python_version=="3.5"
 pytest-httpbin
 
 pep257>=0.6

