Bug 1575135 - Change get_cmd_output to emit unicode strings. r=nalexander

Because most calling places in python configure don't actually want to
deal with encodings, although in practical terms they should, make
get_cmd_output handle it itself.

Places that explicitly do want bytes can keep using subprocess directly.

Differential Revision: https://phabricator.services.mozilla.com/D42604

--HG--
extra : moz-landing-system : lando

build/moz.configure/pkg.configure

@@ -71,7 +71,7 @@ def pkg_check_modules(var, package_desc, when=always,
             return True
         log.info("no")
         log_writer = log.warning if allow_missing else log.error
-        with LineIO(lambda l: log_writer(l), 'replace') as o:
+        with LineIO(lambda l: log_writer(l)) as o:
             o.write(stdout)
         if not allow_missing:
             sys.exit(1)

build/moz.configure/toolchain.configure

@@ -603,7 +603,6 @@ def check_compiler(compiler, language, target):
 @imports(_from='__builtin__', _import='open')
 @imports('json')
 @imports('os')
-@imports(_from='mozbuild.util', _import='system_encoding')
 def get_vc_paths(topsrcdir):
     def vswhere(args):
         program_files = (os.environ.get('PROGRAMFILES(X86)') or
@@ -614,9 +613,7 @@ def get_vc_paths(topsrcdir):
                                'Installer', 'vswhere.exe')
         if not os.path.exists(vswhere):
             return []
-        return json.loads(
-            check_cmd_output(vswhere, '-format', 'json', *args)
-            .decode(system_encoding, 'replace'))
+        return json.loads(check_cmd_output(vswhere, '-format', 'json', *args))
 
     for install in vswhere(['-products', '*', '-requires', 'Microsoft.VisualStudio.Component.VC.Tools.x86.x64']):
         path = install['installationPath']

build/moz.configure/util.configure

@@ -26,6 +26,7 @@ def configure_error(message):
 @imports(_from='__builtin__', _import='unicode')
 @imports('subprocess')
 @imports(_from='mozbuild.shellutil', _import='quote')
+@imports(_from='mozbuild.util', _import='system_encoding')
 def get_cmd_output(*args, **kwargs):
     # subprocess on older Pythons can't handle unicode keys or values in
     # environment dicts. Normalize automagically so callers don't have to
@@ -53,6 +54,8 @@ def get_cmd_output(*args, **kwargs):
                             close_fds=os.name != 'nt',
                             **kwargs)
     stdout, stderr = proc.communicate()
+    stdout = stdout.decode(system_encoding, 'replace')
+    stderr = stderr.decode(system_encoding, 'replace')
     return proc.wait(), stdout, stderr
 
 
@@ -75,7 +78,7 @@ def check_cmd_output(*args, **kwargs):
         for out, desc in ((stdout, 'output'), (stderr, 'error output')):
             if out:
                 log.debug('Its %s was:', desc)
-                with LineIO(lambda l: log.debug('| %s', l), 'replace') as o:
+                with LineIO(lambda l: log.debug('| %s', l)) as o:
                     o.write(out)
         if onerror:
             return onerror()