Log Message:
libsecret: update to 0.18.6.

0.18.6
 * Fix shared key derivation between libsecret and gnome-keyring [#778357]
 * Avoid run-time error when gnome-keyring is not responding [#787391]
 * Enable cross compilation [#748111]
 * Port build scripts to Python 3 [#687637]
 * Build and test fixes [#767002, #777826, #734630, #768112]
 * GI annotation fixes [#785034]
 * Fix textual typos [#782206, ...]
 * Updated translations