Cache /etc/debian_version content (#351)

Author: HorlogeSkynet

distro.py

@@ -868,11 +868,7 @@ def version(self, pretty=False, best=False):
         ]
         if self.id() == "debian" or "debian" in self.like().split():
             # On Debian-like, add debian_version file content to candidates list.
-            try:
-                with open(os.path.join(self.etc_dir, "debian_version")) as fp:
-                    versions.append(fp.readline().rstrip())
-            except IOError:
-                pass
+            versions.append(self._debian_version)
         version = ""
         if best:
             # This algorithm uses the last version in priority order that has
@@ -1199,6 +1195,15 @@ def _uname_info(self):
         content = self._to_str(stdout).splitlines()
         return self._parse_uname_content(content)
 
+    @cached_property
+    def _debian_version(self):
+        # type: () -> str
+        try:
+            with open(os.path.join(self.etc_dir, "debian_version")) as fp:
+                return fp.readline().rstrip()
+        except (OSError, IOError):
+            return ""
+
     @staticmethod
     def _parse_uname_content(lines):
         # type: (Sequence[str]) -> Dict[str, str]

tests/test_distro.py

@@ -2258,7 +2258,7 @@ def test_repr(self):
         repr_str = repr(distro._distro)
         assert "LinuxDistribution" in repr_str
         for attr in MODULE_DISTRO.__dict__.keys():
-            if attr in ("root_dir", "etc_dir", "usr_lib_dir"):
+            if attr in ("root_dir", "etc_dir", "usr_lib_dir", "_debian_version"):
                 continue
             assert attr + "=" in repr_str