Make netifaces optional

netifaces is a binary Python extension. Outside of the installer, it's
only used by CheckedIPAddress.get_matching_interface, which is only
called from installer code.

Make the import of netifaces optional to reduce the amount of
dependencies for PyPI package use case. Binary extensions are especially
annoying, because they depend on shared libraries, compiler, and header
files to be present.

Related: https://pagure.io/freeipa/issue/6468
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Oleg Kozlov <okozlov@redhat.com>

ipapython/ipautil.py

@@ -34,7 +34,6 @@ import socket
 import re
 import datetime
 import netaddr
-import netifaces
 import time
 import pwd
 import grp
@@ -49,6 +48,11 @@ from dns.exception import DNSException
 import six
 from six.moves import input
 
+try:
+    import netifaces
+except ImportError:
+    netifaces = None
+
 from ipapython.dn import DN
 
 logger = logging.getLogger(__name__)
@@ -197,6 +201,8 @@ class CheckedIPAddress(UnsafeIPAddress):
         :return: InterfaceDetails named tuple or None if no interface has
         this address
         """
+        if netifaces is None:
+            raise ImportError("netifaces")
         logger.debug("Searching for an interface of IP address: %s", self)
         if self.version == 4:
             family = netifaces.AF_INET

ipapython/setup.py

@@ -43,11 +43,12 @@ if __name__ == '__main__':
             # "ipalib",  # circular dependency
             "ipaplatform",
             "netaddr",
-            "netifaces",
             "python-ldap",
             "six",
         ],
         extras_require={
             "install": ["dbus-python"],  # for certmonger
+            # CheckedIPAddress.get_matching_interface
+            "netifaces": ["netifaces"],
         },
     )