stick to using easy_install for installing vsc-install, otherwise we end up with vsc.* namespace troubles

lib/vsc/install/ci.py

@@ -33,6 +33,8 @@
 import logging
 import os
 
+from vsc.install.shared_setup import MAX_SETUPTOOLS_VERSION
+
 
 JENKINSFILE = 'Jenkinsfile'
 TOX_INI = 'tox.ini'
@@ -79,10 +81,17 @@ def gen_tox_ini():
         "skip_missing_interpreters = true",
         '',
         '[testenv]',
+        "commands_pre =",
+        # install required setuptools version;
+        # we need a setuptools < 42.0 for now, since in 42.0 easy_install was changed to use pip when available;
+        # it's important to use pip (not easy_install) here, since only pip will actually remove an older
+        # already installed setuptools version
+        "    pip install 'setuptools<%s'" % MAX_SETUPTOOLS_VERSION,
         # install latest vsc-install release from PyPI;
-        # it's important to use pip (not easy_install) here, because vsc-install may require a specific
-        # version of setuptools for example (and only pip will actually remove an older already installed version)
-        "commands_pre = pip install -U vsc-install",
+        # we can't use 'pip install' here, because then we end up with a broken installation because
+        # vsc/__init__.py is not installed because we're using pkg_resources.declare_namespace
+        # (see https://github.com/pypa/pip/issues/1924)
+        "    python -m easy_install -U vsc-install",
         "commands = python setup.py test",
         # $USER is not defined in tox environment, so pass it
         # see https://tox.readthedocs.io/en/latest/example/basic.html#passing-down-environment-variables

lib/vsc/install/shared_setup.py

@@ -159,7 +159,7 @@ def _log(self, level, msg, args):
 
 RELOAD_VSC_MODS = False
 
-VERSION = '0.13.4'
+VERSION = '0.13.5'
 
 log.info('This is (based on) vsc.install.shared_setup %s' % VERSION)
 log.info('(using setuptools version %s located at %s)' % (setuptools.__version__, setuptools.__file__))
@@ -1555,6 +1555,8 @@ def action_target(package, *args, **kwargs):
     _fvs('action_target function')().action_target(package, *args, **kwargs)
 
 
+MAX_SETUPTOOLS_VERSION = '42.0'
+
 if __name__ == '__main__':
     """
     This main is the setup.py for vsc-install
@@ -1563,7 +1565,7 @@ def action_target(package, *args, **kwargs):
         # setuptools 42.0 changed easy_install to use pip if it's available,
         # but vsc-install relies on the setuptools' behaviour of ignoring failing dependency installations and
         # just continuing with the next entry in dependency_links
-        'setuptools<42.0',
+        'setuptools<%s' % MAX_SETUPTOOLS_VERSION,
         'mock',
     ]
 

test/ci.py

@@ -76,7 +76,9 @@ def test_tox_ini(self):
                 "skip_missing_interpreters = true",
                 '',
                 "[testenv]",
-                "commands_pre = pip install -U vsc-install",
+                "commands_pre =",
+                "    pip install 'setuptools<42.0'",
+                "    python -m easy_install -U vsc-install",
                 "commands = python setup.py test",
                 "passenv = USER",
                 '',

tox.ini

@@ -8,7 +8,9 @@ skipsdist = true
 skip_missing_interpreters = true
 
 [testenv]
-commands_pre = pip install -U vsc-install
+commands_pre =
+    pip install 'setuptools<42.0'
+    python -m easy_install -U vsc-install
 commands = python setup.py test
 passenv = USER