close more filehandles with context managers

src/allmydata/node.py

@@ -127,7 +127,8 @@ class Node(service.MultiService):
         self.config_fname = os.path.join(self.basedir, "tahoe.cfg")
         self._portnumfile = os.path.join(self.basedir, self.PORTNUMFILE)
         fileutil.make_dirs(os.path.join(self.basedir, "private"), 0700)
-        open(os.path.join(self.basedir, "private", "README"), "w").write(PRIV_README)
+        with open(os.path.join(self.basedir, "private", "README"), "w") as f:
+            f.write(PRIV_README)
 
         # creates self.config
         self.read_config()
@@ -497,7 +498,8 @@ class Node(service.MultiService):
         return it.
         """
         privname = os.path.join(self.basedir, "private", name)
-        open(privname, "w").write(value)
+        with open(privname, "w") as f:
+            f.write(value)
 
     def get_private_config(self, name, default=_None):
         """Read the (string) contents of a private config file (which is a

src/allmydata/scripts/create_node.py

@@ -218,12 +218,9 @@ def create_node(config):
         os.mkdir(basedir)
     write_tac(basedir, "client")
 
-    c = open(os.path.join(basedir, "tahoe.cfg"), "w")
-
-    write_node_config(c, config)
-    write_client_config(c, config)
-
-    c.close()
+    with open(os.path.join(basedir, "tahoe.cfg"), "w") as c:
+        write_node_config(c, config)
+        write_client_config(c, config)
 
     from allmydata.util import fileutil
     fileutil.make_dirs(os.path.join(basedir, "private"), 0700)

src/allmydata/scripts/startstop_node.py

@@ -183,7 +183,8 @@ def stop(config):
         # we define rc=2 to mean "nothing is running, but it wasn't me who
         # stopped it"
         return 2
-    pid = open(pidfile, "r").read()
+    with open(pidfile, "r") as f:
+        pid = f.read()
     pid = int(pid)
 
     # kill it hard (SIGKILL), delete the twistd.pid file, then wait for the