Merge ~raharper/curtin:fix-missing-zfs-supported-mock into curtin:master

[Ryan Harper]

Don't allow reads of /proc and modprobe zfs through

New zfs_supported check reads /proc/filesystems to see if
zfs is already available and attempts to modprobe. These things
fail under launchpad sbuilds. Make sure to mock out the calls to
these functions and provide positive values for the failing unittest.

[Server Team CI bot (server-team-bot)]

PASSED: Continuous integration, rev:df25e6b718ee803b3fbe496d133a4a35198a7b6e
https://jenkins.ubuntu.com/server/job/curtin-ci/1041/
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    SUCCESS: https://jenkins.ubuntu.com/server/job/curtin-ci/nodes=metal-ppc64el/1041
    SUCCESS: https://jenkins.ubuntu.com/server/job/curtin-ci/nodes=metal-s390x/1041
    SUCCESS: https://jenkins.ubuntu.com/server/job/curtin-ci/nodes=torkoal/1041

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review: Approve (continuous-integration)

[Scott Moser (smoser)]

review: Approve

diff --git a/tests/unittests/test_block_zfs.py b/tests/unittests/test_block_zfs.py
index ca8f118..c18f6a3 100644
--- a/tests/unittests/test_block_zfs.py
+++ b/tests/unittests/test_block_zfs.py
@@ -385,8 +385,13 @@ class TestBlockZfsAssertZfsSupported(CiTestCase):
         self.add_patch('curtin.block.zfs.util.subp', 'mock_subp')
         self.add_patch('curtin.block.zfs.util.get_platform_arch', 'mock_arch')
         self.add_patch('curtin.block.zfs.util.lsb_release', 'mock_release')
-        self.mock_release.return_value = {'codename': 'xenial'}
+        self.add_patch('curtin.block.zfs.util.which', 'mock_which')
+        self.add_patch('curtin.block.zfs.get_supported_filesystems',
+                       'mock_supfs')
         self.mock_arch.return_value = 'x86_64'
+        self.mock_release.return_value = {'codename': 'xenial'}
+        self.mock_supfs.return_value = ['zfs']
+        self.mock_which.return_value = True
 
     def test_supported_arch(self):
         self.assertTrue(zfs.zfs_supported())