Remove pypy and bump py37 to py38

Pypy is not tested in OpenStack anymore,remove the job.

in 'victoria' cycle, we should test py38 by default.
and remove redundant python env.

Change-Id: I8389799ebf2eaa95324b1dc532ef4398ee3094da

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 2.0
-envlist = py37,pypy,pep8
+envlist = py38,pep8
 skipsdist = True
 
 [testenv]
@@ -25,14 +25,6 @@ deps =
   -r{toxinidir}/test-requirements.txt
 commands = bandit -r magnumclient -x tests -n5 -ll
 
-[testenv:pypy]
-basepython = python3
-deps =
-       -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
-       setuptools<3.2
-       -r{toxinidir}/requirements.txt
-       -r{toxinidir}/test-requirements.txt
-
 [testenv:debug]
 basepython = python3
 commands = oslo_debug_helper -t magnumclient/tests {posargs}