Catkin工具给出：“{！r}”.format（fileobj））from None语法错误

Question

最近我安装了柳絮工具。我的系统（Ubuntu18.04）上安装了ros（melodic）。问题是我可以使用catkin_init_工作区，但不能使用catkin init。使用catkin_init或catkin工具的任何命令都会给我一个错误，asyncio丢失了。因此，我使用pip安装了asyncio，但现在我遇到了以下错误：

Traceback (most recent call last):
File "/home/comp/.local/bin/catkin", line 11, in <module>
load_entry_point('catkin-tools==0.4.5', 'console_scripts', 'catkin')()
File "/home/comp/.local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 489, in load_entry_point
return get_distribution(dist).load_entry_point(group, name)
File "/home/comp/.local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2852, in load_entry_point
return ep.load()
File "/home/comp/.local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2443, in load
return self.resolve()
File "/home/comp/.local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2449, in resolve
module = __import__(self.module_name, fromlist=['__name__'], level=0)
File "/home/comp/.local/lib/python2.7/site-packages/catkin_tools/commands/catkin.py", line 28, in <module>
from catkin_tools.common import is_tty
File "/home/comp/.local/lib/python2.7/site-packages/catkin_tools/common.py", line 24, in <module>
import asyncio
File "/home/comp/.local/lib/python2.7/site-packages/asyncio/__init__.py", line 9, in <module>
from . import selectors
File "/home/comp/.local/lib/python2.7/site-packages/asyncio/selectors.py", line 39
"{!r}".format(fileobj)) from None
                           ^
SyntaxError: invalid syntax

以下是我为获得此错误所做的操作：

我刚刚创建了一个包含src目录的目录，然后运行：

catkin init

显然，catkin_init_工作区工作正常。 另外，在这里，我按照说明安装了catkin工具：

https://catkin-tools.readthedocs.io/en/latest/installing.html

这是我用来安装asyncio的命令：

pip uninstall asyncio

我在catkin build中也遇到了这个错误，因为catkin_make工作正常（基本上catkin工具会给出这个错误）。我认为这与python版本或其他东西有关。感谢您的帮助