Add a warning message at end of hang_analyzer.py if a ptrace error occurs in GDB on Linux

If we run the hang_analyzer.py without sudo or with ptrace restriction enabled then GDB may not be able to attach to processes. We should dump a warning message to the effect that the user has to use sudo, or change their configuration to have kernel.yama.ptrace_scope = 0 in the /etc/sysctl.d/10-ptrace.conf file. Could also temporarily disable ptrace restriction with echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope