Error in 'blog' demo --- can't open blog.py

Start in demos/blog and reproduce the failure with docker-compose up, then compare the iptables error with the linked Moby issue. Determine whether the failure belongs to the demo configuration or the host Docker/iptables setup; done means the cause and a reproducible project-level fix are established, or the issue is documented as environmental.

I'm unable to build the 'blog' demo application using docker-compose up. I'm definitely not a docker expert, so it could just be an easy fix.

I try to run docker-compose up in the demos/blog directory, but the build fails because of an unknown option for the iptables command during postgres configuration ( docker0: iptables v1.8.4 (legacy): unknown option "--\dport" ).

Below is the full output from docker-compose up:

[robertc@Z38S blog]$ docker-compose up                                                                                                                                                          
Starting blog_postgres_1 ...                                                                                                                                                                    
WARNING: Host is already in use by another container                                                                                                                                            
                                                                                                                                                                                                
ERROR: for blog_postgres_1  Cannot start service postgres: driver failed programming external connectivity on endpoint blog_postgres_1 (7fc11caf4be5a390d6ccdced928c5ea11d1768090d32b3b0709d41e\
d571e00bd):  (iptables failed: iptables --wait -t nat -A DOCKER -p tcp -d 0/0 --dport 32797 -j DNAT --to-destination 172.17.0.2:3306 ! -i docker0: iptables v1.8.4 (legacy): unknown option "--\
dport"                                                                                                                                                                                          
Try `iptables -h' or 'iptables --help' for more information.                                                                                                                                    
 (exit status 2))                                                                                                                                                                               
                                                                                                                                                                                                
ERROR: for postgres  Cannot start service postgres: driver failed programming external connectivity on endpoint blog_postgres_1 (7fc11caf4be5a390d6ccdced928c5ea11d1768090d32b3b0709d41ed571e00\
bd):  (iptables failed: iptables --wait -t nat -A DOCKER -p tcp -d 0/0 --dport 32797 -j DNAT --to-destination 172.17.0.2:3306 ! -i docker0: iptables v1.8.4 (legacy): unknown option "--dport"  
Try `iptables -h' or 'iptables --help' for more information.                                                                                                                                    
 (exit status 2))                                                                                                                                                                               
ERROR: Encountered errors while bringing up the project.

Edit: This could be related to this issue. I'll check to see if the suggested fix (symlink iptables-nft) works later today.