Make external dependencies optional

This change makes driver dependencies optional thus allowing
sushy-tools to install and run test suite even if some of
these not-always-required dependencies would not otherwise
be met failing the entire installation run.

If the patch is merged, we would need to update sushy-tools
users (mainly, CI jobs) to install the drivers dependencies
of their choice or just all of them.

Story: 2004342
Task: 27929
Change-Id: Ibd05a19d66f372eaa8fc916af98722f7fe701f3c

doc/source/install/index.rst

@@ -15,3 +15,18 @@ Or, if you have virtualenvwrapper installed:
 
    $ mkvirtualenv sushy-tools
    $ pip install sushy-tools
+
+The *Virtual Redfish BMC* tool relies upon one or more hypervisors to mimic
+bare metal nodes. Depending on the virtualization backend you are planning
+to use, certain third-party dependencies should also be installed.
+
+The dependencies for the virtualization backends that should be installed
+for the corresponding drivers to become operational are:
+
+* `libvirt-python` for the libvirt driver
+* `openstacksdk` for the nova driver
+
+.. note::
+
+   The dependencies for at least one virtualization backend should be
+   satisfied to have *Virtual Redfish BMC* emulator operational.

requirements.txt

@@ -4,5 +4,3 @@
 
 pbr!=2.1.0,>=2.0.0 # Apache-2.0
 Flask>=1.0.2 # BSD
-libvirt-python!=4.1.0,>=3.5.0 # LGPLv2+
-openstacksdk>=0.11.2  # Apache-2.0

sushy_tools/emulator/drivers/libvirtdriver.py

@@ -19,7 +19,14 @@ from collections import namedtuple
 from sushy_tools.emulator.drivers.base import AbstractDriver
 from sushy_tools.error import FishyError
 
-import libvirt
+try:
+    import libvirt
+
+except ImportError:
+    libvirt = None
+
+
+is_loaded = bool(libvirt)
 
 BiosProcessResult = namedtuple('BiosProcessResult',
                                ['tree',

sushy_tools/emulator/drivers/novadriver.py

@@ -19,8 +19,14 @@ import math
 from sushy_tools.emulator.drivers.base import AbstractDriver
 from sushy_tools.error import FishyError
 
-import openstack
+try:
+    import openstack
 
+except ImportError:
+    openstack = None
+
+
+is_loaded = bool(openstack)
 
 logger = logging.getLogger(__name__)
 

sushy_tools/emulator/main.py

@@ -20,17 +20,8 @@ import os
 import ssl
 import sys
 
-try:
-    from sushy_tools.emulator.drivers import libvirtdriver
-
-except ImportError:
-    libvirtdriver = None
-
-try:
-    from sushy_tools.emulator.drivers import novadriver
-
-except ImportError:
-    novadriver = None
+from sushy_tools.emulator.drivers import libvirtdriver
+from sushy_tools.emulator.drivers import novadriver
 
 import flask
 
@@ -50,14 +41,14 @@ def init_virt_driver(decorated_func):
         if driver is None:
 
             if 'OS_CLOUD' in os.environ:
-                if not novadriver:
+                if not novadriver.is_loaded:
                     app.logger.error('Nova driver not loaded')
                     sys.exit(1)
 
                 driver = novadriver.OpenStackDriver(os.environ['OS_CLOUD'])
 
             else:
-                if not libvirtdriver:
+                if not libvirtdriver.is_loaded:
                     app.logger.error('libvirt driver not loaded')
                     sys.exit(1)
 
@@ -294,14 +285,14 @@ def main():
     args = parse_args()
 
     if args.os_cloud:
-        if not novadriver:
+        if not novadriver.is_loaded:
             app.logger.error('Nova driver not loaded')
             return 1
 
         driver = novadriver.OpenStackDriver(args.os_cloud)
 
     else:
-        if not libvirtdriver:
+        if not libvirtdriver.is_loaded:
             app.logger.error('libvirt driver not loaded')
             return 1
 

sushy_tools/tests/unit/emulator/test_libvirt.py

@@ -11,7 +11,6 @@
 #    under the License.
 
 import libvirt
-
 from oslotest import base
 from six.moves import mock
 
@@ -26,8 +25,6 @@ class EmulatorTestCase(base.BaseTestCase):
     def setUp(self):
         self.app = main.app.test_client()
 
-        # This enables libvirt driver
-        main.driver = None
         self.test_driver = LibvirtDriver()
         super(EmulatorTestCase, self).setUp()
 

test-requirements.txt

@@ -5,9 +5,13 @@
 hacking>=1.0.0,<1.2.0 # Apache-2.0
 
 coverage!=4.4,>=4.0 # Apache-2.0
+# used by libvirt driver
+libvirt-python!=4.1.0,>=3.5.0 # LGPLv2+
 python-subunit>=1.0.0 # Apache-2.0/BSD
 sphinx!=1.6.6,>=1.6.2 # BSD
 openstackdocstheme>=1.18.1 # Apache-2.0
+# used by nova driver
+openstacksdk>=0.11.2  # Apache-2.0
 oslotest>=3.2.0 # Apache-2.0
 stestr>=1.0.0 # Apache-2.0
 testscenarios>=0.4 # Apache-2.0/BSD