refactor(async): Various edits

Remove reader/writer parameters from AAA methods
Refactor flow_control decorator, as we are no more passing reader/writer instances
Refactor tests

tacacs_plus/async_client.py

@@ -89,32 +89,24 @@ def version(self):
         return (self.version_max * 0x10) + self.version_min
 
     @contextlib.asynccontextmanager
-    async def flow_control(self, reader=None, writer=None):
-        # we do not need to create new reader/writer instances
-        # if both are provided
-        existing = bool(reader and writer)
-        if existing:
-            yielded_reader, yielded_writer = reader, writer
+    async def flow_control(self):
+        if self.family == socket.AF_INET:
+            conn = (self.host, self.port)
         else:
-            if self.family == socket.AF_INET:
-                conn = (self.host, self.port)
-            else:
-                # For AF_INET6 address family, a four-tuple (host, port,
-                # flowinfo, scopeid) is used
-                conn = (self.host, self.port, 0, 0)
-            sock = socket.socket(self.family, socket.SOCK_STREAM)
-            sock.settimeout(self.timeout)
-            sock.connect(conn)
-            yielded_reader, yielded_writer = await asyncio.open_connection(sock=sock)
+            # For AF_INET6 address family, a four-tuple (host, port,
+            # flowinfo, scopeid) is used
+            conn = (self.host, self.port, 0, 0)
+        sock = socket.socket(self.family, socket.SOCK_STREAM)
+        sock.settimeout(self.timeout)
+        sock.connect(conn)
+
+        reader, writer = await asyncio.open_connection(sock=sock)
         try:
-            yield yielded_reader, yielded_writer
+            yield reader, writer
         finally:
-            if not existing:
-                # if reader/writer were not provided -
-                # we need to properly close socket and writer
-                yielded_writer.close()
-                await yielded_writer.wait_closed()
-                sock.close()
+            writer.close()
+            await writer.wait_closed()
+            sock.close()
 
     async def send(self, body, req_type, seq_no=1, reader=None, writer=None):
         """
@@ -191,8 +183,6 @@ async def authenticate(
         chap_challenge=None,
         rem_addr=TAC_PLUS_VIRTUAL_REM_ADDR,
         port=TAC_PLUS_VIRTUAL_PORT,
-        reader=None,
-        writer=None
     ):
         """
         Authenticate to a TACACS+ server with a username and password.
@@ -207,8 +197,6 @@ async def authenticate(
         :param chap_challenge: challenge value when authen_type == 'chap'
         :param rem_addr:       AAA request source, default to TAC_PLUS_VIRTUAL_REM_ADDR
         :param port:           AAA port, default to TAC_PLUS_VIRTUAL_PORT
-        :param reader:         asyncio.StreamReader instance
-        :param writer:         asyncio.StreamWriter instance
         :return:               TACACSAuthenticationReply
         :raises:               socket.timeout, socket.error
         """
@@ -234,7 +222,7 @@ async def authenticate(
                 start_data += chap_challenge.encode()
                 data_to_md5 = (chap_ppp_id + password + chap_challenge).encode()
                 start_data += md5(data_to_md5).digest()
-        async with self.flow_control(reader, writer) as (reader, writer):
+        async with self.flow_control() as (reader, writer):
             packet = await self.send(
                 TACACSAuthenticationStart(
                     username,
@@ -283,8 +271,6 @@ async def authorize(
         priv_lvl=TAC_PLUS_PRIV_LVL_MIN,
         rem_addr=TAC_PLUS_VIRTUAL_REM_ADDR,
         port=TAC_PLUS_VIRTUAL_PORT,
-        reader=None,
-        writer=None
     ):
         """
         Authorize with a TACACS+ server.
@@ -297,14 +283,12 @@ async def authorize(
         :param priv_lvl:       Minimal Required priv_lvl.
         :param rem_addr:       AAA request source, default to TAC_PLUS_VIRTUAL_REM_ADDR
         :param port:           AAA port, default to TAC_PLUS_VIRTUAL_PORT
-        :param reader:         asyncio.StreamReader instance
-        :param writer:         asyncio.StreamWriter instance
         :return:               TACACSAuthenticationReply
         :raises:               socket.timeout, socket.error
         """
         if arguments is None:
             arguments = []
-        async with self.flow_control(reader, writer) as (reader, writer):
+        async with self.flow_control() as (reader, writer):
             packet = await self.send(
                 TACACSAuthorizationStart(
                     username,
@@ -349,8 +333,6 @@ async def account(
         priv_lvl=TAC_PLUS_PRIV_LVL_MIN,
         rem_addr=TAC_PLUS_VIRTUAL_REM_ADDR,
         port=TAC_PLUS_VIRTUAL_PORT,
-        reader=None,
-        writer=None
     ):
         """
         Account with a TACACS+ server.
@@ -366,14 +348,12 @@ async def account(
         :param priv_lvl:       Minimal Required priv_lvl.
         :param rem_addr:       AAA request source, default to TAC_PLUS_VIRTUAL_REM_ADDR
         :param port:           AAA port, default to TAC_PLUS_VIRTUAL_PORT
-        :param reader:         asyncio.StreamReader instance
-        :param writer:         asyncio.StreamWriter instance
         :return:               TACACSAccountingReply
         :raises:               socket.timeout, socket.error
         """
         if arguments is None:
             arguments = []
-        async with self.flow_control(reader, writer) as (reader, writer):
+        async with self.flow_control() as (reader, writer):
             packet = await self.send(
                 TACACSAccountingStart(
                     username,