Spurious error about missing ./ca/index.txt.attr

[dev-zero]

After configuration and when running caman init, I get:

Generating CA private key...
Enter CA password for /user/work/it/caman: 
Generating RSA private key, 4096 bit long modulus
...............................................................................................................................................................++++
.++++
e is 65537 (0x010001)
Signing CA public certificate...
Generating CRL...
Using configuration from /user/work/it/caman/ca/caconfig.cnf
Can't open ./ca/index.txt.attr for reading, No such file or directory
140151468554048:error:02001002:system library:fopen::crypto/bio/bss_file.c:74:fopen('./ca/index.txt.attr','r')
140151468554048:error:2006D080:BIO routines:BIO_new_file:no such file:crypto/bio/bss_file.c:81:
Certificate authority created

while it still worked, this could be worked around by creating the ca/index.txt.attr file manually before, see also this stackoverflow post