ERROR: Rosdep cannot find all required resources to answer your query
I am learning ROS seriously from 2 weeks ago,step by step according to the wiki ROS Tutorials: --installed successfully ROS according to it,with melodic ,with ubuntu 18.04; --just finished successfully "1.Core ROS Tutorials>>1.1 Beginner Level",everythings are OK; Note:During this process, I met some questions, some solved by searching in google.com,baidu.com, etc;others solved by you kind guys,thanks again here.This Q&A is too strong, there are so many kind people to help each other, I believe i will make some great Robots powered by ROS in the future. --begin to study "1.2 Intermediate Level" from today.
Ok,now let me launch my new question: When doing this step: http://wiki.ros.org/ROS/Tutorials/rosdep
$ rosdep install turtlesim
I see:
Command 'rosdep' not found, but can be installed with:
sudo apt install python-rosdep2
Can I do so?
I dare not do so, because I remembered the answers in my other question's several days ago: python-roswtf is the wrong package(it is indeedly true)
and advices: Don’t mix the streams,(see it in http://wiki.ros.org/UpstreamPackages)
I decide to solve it by myself firstly, and I did these things as follows:
$ sudo apt install ros-melodic-rosdep2
E: couldn't location the sw package ros-melodic-rosdep2
$ sudo easy_install -U rosdep rospkg
sudo: easy_install:didn't find this command
$sudo apt-get install python-rosdep
E: couldn't download http://packages.ros.org/ros/ubuntu/po... 404 Not Found [IP: 2600:3404:200:237::2 80] E: There are some sw packages couldn't be downloaded, try apt-get update or add --fix-missing ?
Note:I dare not do so. Considering mybe web connection question, I tried sudo apt-get install python-rosdep for more four times, but failed either.
$ sudo apt-get install python-rosdep2 [sudo] dean pwd: ...... Belows sw packages are auto-installed and not need any more: gcc-4.8-base gdal-data gir1.2-harfbuzz-0.0 google-mock googletest ibverbs-providers icu-devtools libaec0 libapr1-dev libaprutil1-dev libarmadillo8 libarpack2 libasan0 libassuan-dev libavcodec-dev libavformat-dev libavresample-dev libavutil-dev libblas3 libboost-all-dev libboost-atomic-dev libboost-atomic1.65-dev libboost-atomic1.65.1 libboost-chrono-dev libboost-chrono1.65-dev libboost-chrono1.65.1 libboost-container-dev libboost-container1.65-dev libboost-container1.65.1 libboost-context-dev libboost-context1.65-dev libboost-context1.65.1 libboost-coroutine-dev libboost-coroutine1.65-dev libboost-coroutine1.65.1 libboost-date-time-dev libboost-date-time1.65-dev libboost-dev libboost-exception-dev libboost-exception1.65-dev libboost-fiber-dev libboost-fiber1.65-dev libboost-fiber1.65.1 libboost-filesystem-dev libboost-filesystem1.65-dev libboost-graph-dev libboost-graph-parallel-dev libboost-graph-parallel1.65-dev libboost-graph-parallel1.65.1 libboost-graph1.65-dev libboost-graph1.65.1 libboost-iostreams-dev libboost-iostreams1.65-dev libboost-locale-dev libboost-locale1.65-dev libboost-log-dev libboost-log1.65-dev libboost-log1.65.1 libboost-math-dev libboost-math1.65-dev libboost-math1.65.1 libboost-mpi-dev libboost-mpi-python-dev libboost-mpi-python1.65-dev libboost-mpi-python1.65.1 libboost-mpi1.65-dev libboost-mpi1.65.1 libboost-numpy-dev libboost-numpy1.65-dev libboost-numpy1.65.1 libboost-program-options-dev libboost-program-options1.65-dev libboost-program-options1.65.1 libboost-python-dev libboost-python1.65-dev libboost-python1.65.1 libboost-random-dev libboost-random1.65-dev libboost-random1.65.1 libboost-regex-dev libboost-regex1.65-dev libboost-regex1.65.1 libboost-serialization-dev libboost-serialization1.65-dev libboost-serialization1.65.1 libboost-signals-dev libboost-signals1.65-dev libboost-signals1.65.1 libboost-stacktrace-dev libboost-stacktrace1.65-dev libboost-stacktrace1.65.1 libboost-system-dev libboost-system1.65-dev libboost-test-dev libboost-test1.65-dev libboost-test1.65.1 libboost-thread-dev libboost-thread1.65-dev libboost-timer-dev libboost-timer1.65-dev libboost-timer1.65.1 libboost-tools-dev libboost-type-erasure-dev libboost-type-erasure1.65-dev libboost-type-erasure1.65.1 libboost-wave-dev libboost-wave1.65-dev libboost-wave1 ...
$ rosdep update
ERROR: error loading sources list: <urlopen 111]="" <urlopen="" [errno="" connection="" error="" refused=""> (https://raw.githubusercontent.com/ros...></urlopen>