fix: gracefully handle when git executable can't be found (#5988)

* fix: gracefully handle when git executable can't be found

* update test & format

samcli/lib/utils/git_repo.py

@@ -12,6 +12,7 @@
 from subprocess import check_output
 from typing import Optional
 
+from samcli.commands.exceptions import UserException
 from samcli.lib.utils import osutils
 from samcli.lib.utils.osutils import rmtree_callback
 
@@ -36,6 +37,12 @@ class ManifestNotFoundException(Exception):
     """
 
 
+class GitExecutableNotFoundException(UserException):
+    """
+    Used to thrown when git executable not found in the system
+    """
+
+
 class GitRepo:
     """
     Class for managing a Git repo, currently it has a clone functionality only
@@ -83,9 +90,12 @@ def git_executable() -> str:
                     # No exception. Let's pick this
                     return executable
             except OSError as ex:
-                LOG.debug("Unable to find executable %s", executable, exc_info=ex)
+                LOG.warning("Unable to find executable %s", executable, exc_info=ex)
 
-        raise OSError("Cannot find git, was looking at executables: {}".format(executables))
+        raise GitExecutableNotFoundException(
+            "This command requires git but we couldn't find the executable, "
+            f"was looking with following names: {executables}"
+        )
 
     def clone(self, clone_dir: Path, clone_name: str, replace_existing: bool = False, commit: str = "") -> Path:
         """

tests/unit/lib/utils/test_git_repo.py

@@ -3,7 +3,13 @@
 from unittest import TestCase
 from unittest.mock import patch, MagicMock, ANY, call
 import os
-from samcli.lib.utils.git_repo import GitRepo, rmtree_callback, CloneRepoException, CloneRepoUnstableStateException
+from samcli.lib.utils.git_repo import (
+    GitRepo,
+    rmtree_callback,
+    CloneRepoException,
+    CloneRepoUnstableStateException,
+    GitExecutableNotFoundException,
+)
 
 REPO_URL = "REPO URL"
 REPO_NAME = "REPO NAME"
@@ -44,7 +50,7 @@ def test_git_executable_windows(self, mock_platform, mock_popen):
     @patch("samcli.lib.utils.git_repo.subprocess.Popen")
     def test_git_executable_fails(self, mock_popen):
         mock_popen.side_effect = OSError("fail")
-        with self.assertRaises(OSError):
+        with self.assertRaises(GitExecutableNotFoundException):
             self.repo.git_executable()
 
     @patch("samcli.lib.utils.git_repo.Path.exists")