Since PR #1247 we are using the virtual package `.pmbootstrap` to mark
packages as not explcitly installed. In case `pmbootstrap` doesn't
finish the installation because of a bug, the `.pmbootstrap` virtual
package may not get uninstalled.
As virtual packages don't have the "timestamp" attribute set in the
package database (which indicates when the package was built), the
APKINDEX parser fails to parse them.
Changes:
* pmb.parse.apkindex.parse_next_block(): don't require the "timestamp"
attribute to be set (but the arch attribute instead, which is always
present)
* pmb.parse.apkindex.parse(): when a block does not have a `timestamp`
attribute, skip it, because it must be a virtual package.
* add test cases for both functions with a package database that
contains a virtual package.
af4b817c21