解决办法：
- ubuntu18.04：sudo apt install python-rosdep2
- ubuntu20.04：sudo apt install python3-rosdep2
解决办法：
rosdep update失败sudo rm /etc/ros/rosdep/sources.list.d/20-default.list
删除之后重新初始化
原因：https://raw.githubusercontent.com国内无法访问
解决办法（ubuntu18.04涉及python处为python2.7，更高版本为python3）：
- 克隆rosdistro到本地：
git clone https://gitee.com/francois_WAN/rosdistro.git
- 修改20-default.list内的路径变为git的：
cd /home/yourname/rosdistro/rosdep/sources.list.d/
sudo gedit 20-default.list
替换后的内容为（yourname为ubuntu用户名）：
# os-specific listings first yaml file:///home/yourname/rosdistro/rosdep/osx-homebrew.yaml osx # generic yaml file:///home/yourname/rosdistro/rosdep/base.yaml yaml file:///home/yourname/rosdistro/rosdep/python.yaml yaml file:///home/yourname/rosdistro/rosdep/ruby.yaml gbpdistro file:///home/yourname/rosdistro/releases/fuerte.yaml fuerte
-
修改gedit gbpdistro_support.py
cd /usr/lib/python2.7/dist-packages/rosdep2/
sudo gedit gbpdistro_support.py替换内容:
FUERTE_GBPDISTRO_URL = 'file:///home/yourname/rosdistro/'
'releases/fuerte.yaml'
-
修改rep3.py
cd /usr/lib/python2.7/dist-packages/rosdep2/
sudo gedit rep3.py替换内容:
REP3_TARGETS_URL = 'file:///home/yourname/rosdistro/releases/targets.yaml'
-
修改_init_.py
cd /usr/lib/python2.7/dist-packages/rosdistro/
sudo gedit __init__.py替换内容:
DEFAULT_INDEX_URL = 'file:///home/yourname/rosdistro/index-v4.yaml'
-
修改 20-default.list
cd /etc/ros/rosdep/sources.list.d
sudo gedit 20-default.list替换内容:
#os-specific listings first yaml file:///home/yourname/rosdistro/rosdep/osx-homebrew.yaml osx #generic yaml file:///home/yourname/rosdistro/rosdep/base.yaml yaml file:///home/yourname/rosdistro/rosdep/python.yaml yaml file:///home/yourname/rosdistro/rosdep/ruby.yaml gbpdistro file:///home/yourname/rosdistro/releases/fuerte.yaml fuerte #newer distributions (Groovy, Hydro, ...) must not be listed anymore, they are being fetched from the rosdistro index.yaml instead
最后重新rosdep update即可
roscore not found解决办法：重新安装ROS桌面版来补充缺少文件
sudo apt-get install ros-melodic-desktop
然后执行：source ~/.bashrc
