backup: rename pstr() helper to b2s()

The helper is just bytes->str conversion with errors=backslashreplace,
which we can use for more than just paths.

backup.py

@@ -23,8 +23,8 @@ import yaml
 import wcmatch.glob # type: ignore
 import humanfriendly # type: ignore
 
-def pstr(path: bytes) -> str:
-    return path.decode(errors='backslashreplace')
+def b2s(raw: bytes) -> str:
+    return raw.decode(errors='backslashreplace')
 
 def format_size(n: int) -> str:
     return humanfriendly.format_size(n, keep_width=True, binary=True)
@@ -132,7 +132,7 @@ class Backup:
         self.outfile = outfile
         for root in self.config.roots:
             if root in self.root_seen:
-                self.log('I', f"ignoring root, already seen: {pstr(root)}")
+                self.log('I', f"ignoring root, already seen: {b2s(root)}")
                 continue
 
             try:
@@ -140,13 +140,13 @@ class Backup:
                 if not stat.S_ISDIR(st.st_mode):
                     raise NotADirectoryError
             except FileNotFoundError:
-                self.log('E', f"root does not exist: {pstr(root)}")
+                self.log('E', f"root does not exist: {b2s(root)}")
                 continue
             except NotADirectoryError:
-                self.log('E', f"root is not a directory: {pstr(root)}")
+                self.log('E', f"root is not a directory: {b2s(root)}")
                 continue
 
-            self.log('I', f"processing root {pstr(root)}")
+            self.log('I', f"processing root {b2s(root)}")
             self.scan(root)
 
     def scan(self, path: bytes, parent_st: os.stat_result=None):
@@ -199,7 +199,7 @@ class Backup:
             force = self.config.match_re(self.config.unexclude, decorated_path)
             if exclude_reason and not force:
                 self.log(exclude_reason[0],
-                         f"{exclude_reason[1]}: {pstr(path)}")
+                         f"{exclude_reason[1]}: {b2s(path)}")
                 return
 
             # Print path for Borg
@@ -221,7 +221,7 @@ class Backup:
                         with open(path + b'/CACHEDIR.TAG', 'rb') as f:
                             if f.read(len(tag)) == tag:
                                 self.log(
-                                    'I', f"skipping, cache dir: {pstr(path)}")
+                                    'I', f"skipping, cache dir: {b2s(path)}")
                                 return
                     except:
                         pass
@@ -235,7 +235,7 @@ class Backup:
                 IsADirectoryError,
                 NotADirectoryError,
                 PermissionError) as e:
-            self.log('E', f"can't read {pstr(path)}: {str(e)}")
+            self.log('E', f"can't read {b2s(path)}: {str(e)}")
             return
 
     def run_borg(self, argv: typing.List[str],