[PATCH 2 of 3 v3] dev_requirements.txt: bump minimum pytest versions to a working set

[Thomas De Schampheleire]

# HG changeset patch
# User Thomas De Schampheleire <thomas.de_schampheleire at nokia.com>
# Date 1572118519 -7200
#      Sat Oct 26 21:35:19 2019 +0200
# Node ID 9de1b85832bfb6cda95da1812c732000920c3295
# Parent  024bd5ab79e219965015fada76a25cf19fce7195
dev_requirements.txt: bump minimum pytest versions to a working set

Not all combinations of pytest-related packages seem to work.
Trial-and-error lead to these combinations of minimum versions.

Add a minimum bound to pytest-benchmark and pytest-localserver to help pip
in figuring out a suitable combination with pytest, and also to allow
testing minimum combinations in the future.

Drop pytest-runner, which should not be needed unless when running tests
directly from setup.py.

diff --git a/dev_requirements.txt b/dev_requirements.txt
--- a/dev_requirements.txt
+++ b/dev_requirements.txt
@@ -1,8 +1,7 @@
-pytest >= 3.3.0, < 4.7
-pytest-runner < 5.2
-pytest-sugar >= 0.7.0, < 0.10
-pytest-benchmark < 3.3
-pytest-localserver < 0.6
+pytest >= 4.6.6, < 4.7
+pytest-sugar >= 0.9.2, < 0.10
+pytest-benchmark >= 3.2.2, < 3.3
+pytest-localserver >= 0.5.0, < 0.6
 mock < 3.1
 Sphinx < 1.9
 WebTest < 2.1