Typo in globus_gsi_system_config.c

[fscheiner]

Detected by chance. There is a superfluous comma here:

https://github.com/gridcf/gct/blob/aed61ccce4b376c5a0107d72fec777b1824e3461/gsi/sysconfig/source/library/globus_gsi_system_config.c#L1901-L1910

...that is not present for the case when the cert file is missing:

.globus/userkey.pem missing, .globus/usercert.pem present

$ grid-proxy-init -debug
Error: Couldn't find valid credentials to generate a proxy.
       grid_proxy_init.c:535: globus_sysconfig: Error with key filename: The user key could not be found in:
,1) env. var. X509_USER_KEY
2) $HOME/.globus/userkey.pem
3) $HOME/.globus/usercred.p12

.globus/userkey.pem present, .globus/usercert.pem missing

$ grid-proxy-init -debug
Error: Couldn't find valid credentials to generate a proxy.
       grid_proxy_init.c:535: globus_sysconfig: Error with certificate filename: The user cert could not be found in: 
1) env. var. X509_USER_CERT
2) $HOME/.globus/usercert.pem
3) $HOME/.globus/usercred.p12

[fscheiner]

Fixed with #218.