Works for me:

+ VENV_VERSION=15.0.3                                    
++ timer_start                                                                                                                                                                      
++ timer=0                                                                                                                                                          
+ wget https://github.com/pypa/virtualenv/archive/15.0.3.tar.gz             
--2018-05-30 10:00:48--  https://github.com/pypa/virtualenv/archive/15.0.3.tar.gz                                                                                                   
Resolving github.com (github.com)... 192.30.253.112, 192.30.253.113                                                                                           
Connecting to github.com (github.com)|192.30.253.112|:443... connected.                                                                                                             
HTTP request sent, awaiting response... 302 Found                                                                
Location: https://codeload.github.com/pypa/virtualenv/tar.gz/15.0.3 [following]                                                                                           
--2018-05-30 10:00:48--  https://codeload.github.com/pypa/virtualenv/tar.gz/15.0.3                                                                                                  
Resolving codeload.github.com (codeload.github.com)... 192.30.253.121, 192.30.253.120                 
Connecting to codeload.github.com (codeload.github.com)|192.30.253.121|:443... connected.                                                                                           
HTTP request sent, awaiting response... 200 OK                                                                   
Length: unspecified [application/x-gzip]                       
Saving to: ‘15.0.3.tar.gz’                                                                                                                                                          
                                                             
15.0.3.tar.gz                                     [   <=>                                                                                         ]   1.76M  3.32MB/s    in 0.5s    
                                                                                                                                                   
2018-05-30 10:00:49 (3.32 MB/s) - ‘15.0.3.tar.gz’ saved [1847120]                                                                                                                   
                                                                           
++ timer_start                                                                                                                                                                       
++ timer=0                                                                            
+ tar xvfz 15.0.3.tar.gz                                                                                                                                  
virtualenv-15.0.3/                                                                                                                                                                   
virtualenv-15.0.3/.gitattributes                                                                                                                                                     
virtualenv-15.0.3/.gitignore                                                                                                                                                        
virtualenv-15.0.3/.travis.yml                                                       
virtualenv-15.0.3/AUTHORS.txt