issue #408: 2.4 compat: replace iter_read with explicit generator

Can't use yield inside try/finally on 2.4.

mitogen/parent.py

@@ -505,6 +505,48 @@ def write_all(fd, s, deadline=None):
         poller.close()
 
 
+class IteratingRead(object):
+    def __init__(self, fds, deadline=None):
+        self.deadline = deadline
+        self.poller = PREFERRED_POLLER()
+        for fd in fds:
+            self.poller.start_receive(fd)
+
+        self.bits = []
+        self.timeout = None
+
+    def close(self):
+        self.poller.close()
+
+    def __iter__(self):
+        return self
+
+    def next(self):
+        while self.poller.readers:
+            if self.deadline is not None:
+                timeout = max(0, self.deadline - time.time())
+                if timeout == 0:
+                    break
+
+            for fd in self.poller.poll(timeout):
+                s, disconnected = mitogen.core.io_op(os.read, fd, 4096)
+                if disconnected or not s:
+                    IOLOG.debug('iter_read(%r) -> disconnected', fd)
+                    self.poller.stop_receive(fd)
+                else:
+                    IOLOG.debug('iter_read(%r) -> %r', fd, s)
+                    self.bits.append(s)
+                    return s
+
+        if not poller.readers:
+            raise EofError(u'EOF on stream; last 300 bytes received: %r' %
+                           (b('').join(self.bits)[-300:].decode('latin1'),))
+
+        raise mitogen.core.TimeoutError('read timed out')
+
+    __next__ = next
+
+
 def iter_read(fds, deadline=None):
     """Return a generator that arranges for up to 4096-byte chunks to be read
     at a time from the file descriptor `fd` until the generator is destroyed.
@@ -522,36 +564,7 @@ def iter_read(fds, deadline=None):
     :raises mitogen.core.StreamError:
         Attempt to read past end of file.
     """
-    poller = PREFERRED_POLLER()
-    for fd in fds:
-        poller.start_receive(fd)
-
-    bits = []
-    timeout = None
-    try:
-        while poller.readers:
-            if deadline is not None:
-                timeout = max(0, deadline - time.time())
-                if timeout == 0:
-                    break
-
-            for fd in poller.poll(timeout):
-                s, disconnected = mitogen.core.io_op(os.read, fd, 4096)
-                if disconnected or not s:
-                    IOLOG.debug('iter_read(%r) -> disconnected', fd)
-                    poller.stop_receive(fd)
-                else:
-                    IOLOG.debug('iter_read(%r) -> %r', fd, s)
-                    bits.append(s)
-                    yield s
-    finally:
-        poller.close()
-
-    if not poller.readers:
-        raise EofError(u'EOF on stream; last 300 bytes received: %r' %
-                       (b('').join(bits)[-300:].decode('latin1'),))
-
-    raise mitogen.core.TimeoutError('read timed out')
+    return IteratingRead(fds=fds, deadline=deadline)
 
 
 def discard_until(fd, s, deadline):