[3/8] fetch2: Check for git-lfs existence before using it

diff --git a/lib/bb/fetch2/git.py b/lib/bb/fetch2/git.py
index 39c183927..b32b18797 100644
--- a/lib/bb/fetch2/git.py
+++ b/lib/bb/fetch2/git.py
@@ -324,6 +324,11 @@  class Git(FetchMethod):
         return False
 
     def lfs_need_update(self, ud, d):
+        if not self._need_lfs(ud):
+            return False
+
+        self._ensure_git_lfs(d, ud)
+
         if self.clonedir_need_update(ud, d):
             return True
 
@@ -507,7 +512,9 @@  class Git(FetchMethod):
     def lfs_fetch(self, ud, d, clonedir, revision, fetchall=False, progresshandler=None):
         """Helper method for fetching Git LFS data"""
         try:
-            if self._need_lfs(ud) and self._contains_lfs(ud, d, clonedir) and self._find_git_lfs(d) and len(revision):
+            if self._need_lfs(ud) and self._contains_lfs(ud, d, clonedir) and len(revision):
+                self._ensure_git_lfs(d, ud)
+
                 # Using worktree with the revision because .lfsconfig may exists
                 worktree_add_cmd = "%s worktree add wt %s" % (ud.basecmd, revision)
                 runfetchcmd(worktree_add_cmd, d, log=progresshandler, workdir=clonedir)
@@ -740,11 +747,11 @@  class Git(FetchMethod):
         runfetchcmd("%s remote set-url origin %s" % (ud.basecmd, shlex.quote(repourl)), d, workdir=destdir)
 
         if self._contains_lfs(ud, d, destdir):
-            if need_lfs and not self._find_git_lfs(d):
-                raise bb.fetch2.FetchError("Repository %s has LFS content, install git-lfs on host to download (or set lfs=0 to ignore it)" % (repourl))
-            elif not need_lfs:
+            if not need_lfs:
                 bb.note("Repository %s has LFS content but it is not being fetched" % (repourl))
             else:
+                self._ensure_git_lfs(d, ud)
+
                 runfetchcmd("%s lfs install --local" % ud.basecmd, d, workdir=destdir)
 
         if not ud.nocheckout:
@@ -807,7 +814,7 @@  class Git(FetchMethod):
         Verifies whether the LFS objects for requested revisions have already been downloaded
         """
         # Bail out early if this repository doesn't use LFS
-        if not self._need_lfs(ud) or not self._contains_lfs(ud, d, wd):
+        if not self._contains_lfs(ud, d, wd):
             return True
 
         # The Git LFS specification specifies ([1]) the LFS folder layout so it should be safe to check for file
@@ -859,11 +866,14 @@  class Git(FetchMethod):
             pass
         return False
 
-    def _find_git_lfs(self, d):
+    def _ensure_git_lfs(self, d, ud):
         """
-        Return True if git-lfs can be found, False otherwise.
+        Ensures that git-lfs is available, raising a FetchError if it isn't.
         """
-        return shutil.which("git-lfs", path=d.getVar('PATH')) is not None
+        if shutil.which("git-lfs", path=d.getVar('PATH')) is None:
+            raise bb.fetch2.FetchError(
+                "Repository %s has LFS content, install git-lfs on host to download (or set lfs=0 "
+                "to ignore it)" % self._get_repo_url(ud))
 
     def _get_repo_url(self, ud):
         """
diff --git a/lib/bb/tests/fetch.py b/lib/bb/tests/fetch.py
index f0c628524..a936af6fb 100644
--- a/lib/bb/tests/fetch.py
+++ b/lib/bb/tests/fetch.py
@@ -9,6 +9,7 @@ 
 import contextlib
 import shutil
 import unittest
+import unittest.mock
 import urllib.parse
 import hashlib
 import tempfile
@@ -2413,18 +2414,17 @@  class GitLfsTest(FetcherTest):
         # Careful: suppress initial attempt at downloading
         fetcher, ud = self.fetch(uri=None, download=False)
 
-        # Artificially assert that git-lfs is not installed, so
-        # we can verify a failure to unpack in it's absence.
-        old_find_git_lfs = ud.method._find_git_lfs
-        try:
-            # If git-lfs cannot be found, the unpack should throw an error
+        # If git-lfs cannot be found, the download should throw an error
+        with unittest.mock.patch("shutil.which", return_value=None):
             with self.assertRaises(bb.fetch2.FetchError):
                 fetcher.download()
-                ud.method._find_git_lfs = lambda d: False
+
+        fetcher.download()
+        # If git-lfs cannot be found, the unpack should throw an error
+        with self.assertRaises(bb.fetch2.FetchError):
+            with unittest.mock.patch("shutil.which", return_value=None):
                 shutil.rmtree(self.gitdir, ignore_errors=True)
                 fetcher.unpack(self.d.getVar('WORKDIR'))
-        finally:
-            ud.method._find_git_lfs = old_find_git_lfs
 
     def test_lfs_disabled_not_installed(self):
         uri = 'git://%s;protocol=file;lfs=0;branch=master' % self.srcdir
@@ -2433,17 +2433,11 @@  class GitLfsTest(FetcherTest):
         # Careful: suppress initial attempt at downloading
         fetcher, ud = self.fetch(uri=None, download=False)
 
-        # Artificially assert that git-lfs is not installed, so
-        # we can verify a failure to unpack in it's absence.
-        old_find_git_lfs = ud.method._find_git_lfs
-        try:
-            # Even if git-lfs cannot be found, the unpack should be successful
+        # Even if git-lfs cannot be found, the download / unpack should be successful
+        with unittest.mock.patch("shutil.which", return_value=None):
             fetcher.download()
-            ud.method._find_git_lfs = lambda d: False
             shutil.rmtree(self.gitdir, ignore_errors=True)
             fetcher.unpack(self.d.getVar('WORKDIR'))
-        finally:
-            ud.method._find_git_lfs = old_find_git_lfs
 
 class GitURLWithSpacesTest(FetcherTest):
     test_git_urls = {