Address deprecated warnings with Python 3.8

All these chances work fine with 3.5, our minimally required version.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/libkas.py

@@ -63,14 +63,13 @@ class LogOutput:
         self.stderr.append(line)
 
 
-@asyncio.coroutine
-def _read_stream(stream, callback):
+async def _read_stream(stream, callback):
     """
         This asynchronous method reads from the output stream of the
         application and transfers each line to the callback function.
     """
     while True:
-        line = yield from stream.readline()
+        line = await stream.readline()
         try:
             line = line.decode('utf-8')
         except UnicodeDecodeError as err:
@@ -82,8 +81,7 @@ def _read_stream(stream, callback):
             break
 
 
-@asyncio.coroutine
-def run_cmd_async(cmd, cwd, env=None, fail=True, liveupdate=True):
+async def run_cmd_async(cmd, cwd, env=None, fail=True, liveupdate=True):
     """
         Run a command asynchronously.
     """
@@ -95,7 +93,7 @@ def run_cmd_async(cmd, cwd, env=None, fail=True, liveupdate=True):
     logo = LogOutput(liveupdate)
 
     try:
-        process = yield from asyncio.create_subprocess_exec(
+        process = await asyncio.create_subprocess_exec(
             *cmd,
             cwd=cwd,
             env=env,
@@ -110,11 +108,11 @@ def run_cmd_async(cmd, cwd, env=None, fail=True, liveupdate=True):
             raise ex
         return (errno.EPERM, str(ex))
 
-    yield from asyncio.wait([
+    await asyncio.wait([
         _read_stream(process.stdout, logo.log_stdout),
         _read_stream(process.stderr, logo.log_stderr)
     ])
-    ret = yield from process.wait()
+    ret = await process.wait()
 
     if ret and fail:
         msg = 'Command "{cwd}$ {cmd}" failed'.format(cwd=cwd, cmd=cmdstr)