Enforce E501: Limit the line length to 79 for files in pmb/parse - part 1 (MR 2019)

Made changes to limit the line length in following files,
 - pmb/parse/_apkbuild.py
 - pmb/parse/apkindex.py
 - pmb/parse/binfmt_info.py
 - pmb/parse/deviceinfo.py
 - test/test_parse_apkbuild.py

Added the above files in E501 flake8 command list.
Substitute f-string for string concatenation.

pmb/parse/binfmt_info.py

@@ -26,8 +26,8 @@ def binfmt_info(args, arch_qemu):
     for type in ["mask", "magic"]:
         key = arch_qemu + "_" + type
         if key not in full:
-            raise RuntimeError("Could not find key " + key + " in binfmt info file: " +
-                               info)
+            raise RuntimeError(
+                f"Could not find key {key} in binfmt info file: {info}")
         ret[type] = full[key]
     logging.verbose("=> " + str(ret))
     return ret