util: rename get_architecture to get_dpkg_architecture (#173)

This makes it clearer that we should only use this in code paths that
will definitely have dpkg available to them.

- Rename get_architecture -> get_dpkg_architecture
- Add docstring to get_dpkg_architecture

3 files changed, 10 insertions, 5 deletions

diff --git a/cloudinit/config/cc_apt_configure.py b/cloudinit/config/cc_apt_configure.py
index 4a3aed36..c44dec45 100644
--- a/cloudinit/config/cc_apt_configure.py
+++ b/cloudinit/config/cc_apt_configure.py
@@ -253,7 +253,7 @@ def get_default_mirrors(arch=None, target=None):
        architecture, for more see:
        https://wiki.ubuntu.com/UbuntuDevelopment/PackageArchive#Ports"""
     if arch is None:
-        arch = util.get_architecture(target)
+        arch = util.get_dpkg_architecture(target)
     if arch in PRIMARY_ARCHES:
         return PRIMARY_ARCH_MIRRORS.copy()
     if arch in PORTS_ARCHES:
@@ -303,7 +303,7 @@ def apply_apt(cfg, cloud, target):
     LOG.debug("handling apt config: %s", cfg)
 
     release = util.lsb_release(target=target)['codename']
-    arch = util.get_architecture(target)
+    arch = util.get_dpkg_architecture(target)
     mirrors = find_apt_mirror_info(cfg, cloud, arch=arch)
     LOG.debug("Apt Mirror info: %s", mirrors)
 
@@ -896,7 +896,7 @@ def find_apt_mirror_info(cfg, cloud, arch=None):
     """
 
     if arch is None:
-        arch = util.get_architecture()
+        arch = util.get_dpkg_architecture()
         LOG.debug("got arch for mirror selection: %s", arch)
     pmirror = get_mirror(cfg, "primary", arch, cloud)
     LOG.debug("got primary mirror: %s", pmirror)
diff --git a/cloudinit/distros/debian.py b/cloudinit/distros/debian.py
index 79268371..128bb523 100644
--- a/cloudinit/distros/debian.py
+++ b/cloudinit/distros/debian.py
@@ -205,7 +205,7 @@ class Distro(distros.Distro):
                          ["update"], freq=PER_INSTANCE)
 
     def get_primary_arch(self):
-        return util.get_architecture()
+        return util.get_dpkg_architecture()
 
 
 def _get_wrapper_prefix(cmd, mode):
diff --git a/cloudinit/util.py b/cloudinit/util.py
index 87480767..d99e82fa 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -79,7 +79,12 @@ CONTAINER_TESTS = (['systemd-detect-virt', '--quiet', '--container'],
 
 
 @lru_cache()
-def get_architecture(target=None):
+def get_dpkg_architecture(target=None):
+    """Return the sanitized string output by `dpkg --print-architecture`.
+
+    N.B. This function is wrapped in functools.lru_cache, so repeated calls
+    won't shell out every time.
+    """
     out, _ = subp(['dpkg', '--print-architecture'], capture=True,
                   target=target)
     return out.strip()