[pyupgrade] `synapse/` (#10348)

This PR is tantamount to running 
```
pyupgrade --py36-plus --keep-percent-format `find synapse/ -type f -name "*.py"`
```

Part of #9744

3 files changed, 6 insertions, 8 deletions

diff --git a/synapse/util/caches/lrucache.py b/synapse/util/caches/lrucache.py
index efeba0cb96..5c65d187b6 100644
--- a/synapse/util/caches/lrucache.py
+++ b/synapse/util/caches/lrucache.py
@@ -90,8 +90,7 @@ def enumerate_leaves(node, depth):
         yield node
     else:
         for n in node.values():
-            for m in enumerate_leaves(n, depth - 1):
-                yield m
+            yield from enumerate_leaves(n, depth - 1)
 
 
 P = TypeVar("P")
diff --git a/synapse/util/caches/treecache.py b/synapse/util/caches/treecache.py
index a6df81ebff..4138931e7b 100644
--- a/synapse/util/caches/treecache.py
+++ b/synapse/util/caches/treecache.py
@@ -138,7 +138,6 @@ def iterate_tree_cache_entry(d):
     """
     if isinstance(d, TreeCacheNode):
         for value_d in d.values():
-            for value in iterate_tree_cache_entry(value_d):
-                yield value
+            yield from iterate_tree_cache_entry(value_d)
     else:
         yield d
diff --git a/synapse/util/daemonize.py b/synapse/util/daemonize.py
index 31b24dd188..d8532411c2 100644
--- a/synapse/util/daemonize.py
+++ b/synapse/util/daemonize.py
@@ -31,13 +31,13 @@ def daemonize_process(pid_file: str, logger: logging.Logger, chdir: str = "/") -
     # If pidfile already exists, we should read pid from there; to overwrite it, if
     # locking will fail, because locking attempt somehow purges the file contents.
     if os.path.isfile(pid_file):
-        with open(pid_file, "r") as pid_fh:
+        with open(pid_file) as pid_fh:
             old_pid = pid_fh.read()
 
     # Create a lockfile so that only one instance of this daemon is running at any time.
     try:
         lock_fh = open(pid_file, "w")
-    except IOError:
+    except OSError:
         print("Unable to create the pidfile.")
         sys.exit(1)
 
@@ -45,7 +45,7 @@ def daemonize_process(pid_file: str, logger: logging.Logger, chdir: str = "/") -
         # Try to get an exclusive lock on the file. This will fail if another process
         # has the file locked.
         fcntl.flock(lock_fh, fcntl.LOCK_EX | fcntl.LOCK_NB)
-    except IOError:
+    except OSError:
         print("Unable to lock on the pidfile.")
         # We need to overwrite the pidfile if we got here.
         #
@@ -113,7 +113,7 @@ def daemonize_process(pid_file: str, logger: logging.Logger, chdir: str = "/") -
     try:
         lock_fh.write("%s" % (os.getpid()))
         lock_fh.flush()
-    except IOError:
+    except OSError:
         logger.error("Unable to write pid to the pidfile.")
         print("Unable to write pid to the pidfile.")
         sys.exit(1)