Fix Pop!_OS 20.04 not using aptpkg

changelog/58395.fixed

@@ -0,0 +1 @@
+Pop!_OS 20.04 and 20.10 now support using pkg.* / aptpkg.*

salt/grains/core.py

@@ -1556,6 +1556,7 @@ def id_():
     "slesexpand": "RES",
     "linuxmint": "Mint",
     "neon": "KDE neon",
+    "pop": "Pop",
 }
 
 # Map the 'os' grain to the 'os_family' grain
@@ -1628,6 +1629,7 @@ def id_():
     "Funtoo": "Gentoo",
     "AIX": "AIX",
     "TurnKey": "Debian",
+    "Pop": "Debian",
 }
 
 # Matches any possible format:

tests/unit/grains/test_core.py

@@ -726,6 +726,46 @@ def test_ubuntu_artful_os_grains(self):
         }
         self._run_os_grains_tests("ubuntu-17.10", _os_release_map, expectation)
 
+    @skipIf(not salt.utils.platform.is_linux(), "System is not Linux")
+    def test_pop_focal_os_grains(self):
+        """
+        Test if OS grains are parsed correctly in Pop!_OS 20.04 "Focal Fossa"
+        """
+        _os_release_map = {
+            "_linux_distribution": ("Pop", "20.04", "focal"),
+        }
+        expectation = {
+            "os": "Pop",
+            "os_family": "Debian",
+            "oscodename": "focal",
+            "osfullname": "Pop",
+            "osrelease": "20.04",
+            "osrelease_info": (20, 4),
+            "osmajorrelease": 20,
+            "osfinger": "Pop-20",
+        }
+        self._run_os_grains_tests("pop-20.04", _os_release_map, expectation)
+
+    @skipIf(not salt.utils.platform.is_linux(), "System is not Linux")
+    def test_pop_groovy_os_grains(self):
+        """
+        Test if OS grains are parsed correctly in Pop!_OS 20.10 "Groovy Gorilla"
+        """
+        _os_release_map = {
+            "_linux_distribution": ("Pop", "20.10", "groovy"),
+        }
+        expectation = {
+            "os": "Pop",
+            "os_family": "Debian",
+            "oscodename": "groovy",
+            "osfullname": "Pop",
+            "osrelease": "20.10",
+            "osrelease_info": (20, 10),
+            "osmajorrelease": 20,
+            "osfinger": "Pop-20",
+        }
+        self._run_os_grains_tests("pop-20.10", _os_release_map, expectation)
+
     @skipIf(not salt.utils.platform.is_windows(), "System is not Windows")
     def test_windows_platform_data(self):
         """