Allow foreign::read.dta and foreign::read.spss to fail

[briatte]

Allow calls to foreign to fail when reading ESS data with that instead of haven.

Description

• In order to avoid quitting on an error, the code sends a warning and then returns NULL.
• The warning message suggests trying a different format.

Related Issue

#49

Example

# fails to import as of 2021-04-13
import_sddf_country(country = "Albania", rounds = 6)