build is necessary: better binary > aport message

Clearly state which version is being used, and also display the message
when using build --force.

- Old:
WARNING: Package 'ubuntu-app-launch' in your aports folder has version
0_git20180604-r0, but the binary package repositories already have version
0_p20181101174257-r0! See also: <https://postmarketos.org/warning-repo2>

- New:
WARNING: package hello-world: aport version 1-r4 is lower than 1-r5 from
the binary repository. 1-r5 will be used when installing hello-world.
See also: <https://postmarketos.org/warning-repo2>

pmb/build/_package.py

@@ -143,7 +143,12 @@ def is_necessary_warn_depends(args, apkbuild, arch, force, depends_built):
     :returns: True or False
     """
     pkgname = apkbuild["pkgname"]
-    ret = True if force else pmb.build.is_necessary(args, arch, apkbuild)
+
+    # Check if necessary (this warns about binary version > aport version, so
+    # call it even in force mode)
+    ret = pmb.build.is_necessary(args, arch, apkbuild)
+    if force:
+        ret = True
 
     if not ret and len(depends_built):
         # Warn of potentially outdated package

pmb/build/other.py

@@ -150,10 +150,12 @@ def is_necessary(args, arch, apkbuild, indexes=None):
     # a) Binary repo has a newer version
     version_old = index_data["version"]
     if pmb.parse.version.compare(version_old, version_new) == 1:
-        logging.warning("WARNING: Package '" + package + "' in your aports folder"
-                        " has version " + version_new + ", but the binary package"
-                        " repositories already have version " + version_old + "!"
-                        " See also: <https://postmarketos.org/warning-repo2>")
+        logging.warning("WARNING: package {}: aport version {} is lower than"
+                        " {} from the binary repository. {} will be used when"
+                        " installing {}. See also:"
+                        " <https://postmarketos.org/warning-repo2>"
+                        "".format(package, version_new, version_old,
+                                  version_old, package))
         return False
 
     # b) Aports folder has a newer version