Remove Python 2 support

Python 2 is long dead and devlib does not support it anymore, so cleanup
old Python 2-only code.

wa/framework/getters.py

@@ -244,10 +244,7 @@ class Http(ResourceGetter):
                                              response.status_code,
                                              response.reason))
             return {}
-        if sys.version_info[0] == 3:
-            content = response.content.decode('utf-8')
-        else:
-            content = response.content
+        content = response.content.decode('utf-8')
         return json.loads(content)
 
     def download_asset(self, asset, owner_name):

wa/framework/instrument.py

@@ -325,10 +325,7 @@ def install(instrument, context):
         if not callable(attr):
             msg = 'Attribute {} not callable in {}.'
             raise ValueError(msg.format(attr_name, instrument))
-        if sys.version_info[0] == 3:
-            argspec = inspect.getfullargspec(attr)
-        else:
-            argspec = inspect.getargspec(attr)  # pylint: disable=deprecated-method
+        argspec = inspect.getfullargspec(attr)
         arg_num = len(argspec.args)
         # Instrument callbacks will be passed exactly two arguments: self
         # (the instrument instance to which the callback is bound) and

wa/framework/version.py

@@ -57,7 +57,4 @@ def get_commit():
     p.wait()
     if p.returncode:
         return None
-    if sys.version_info[0] == 3 and isinstance(std, bytes):
-        return std[:8].decode(sys.stdout.encoding or 'utf-8')
-    else:
-        return std[:8]
+    return std[:8].decode(sys.stdout.encoding or 'utf-8')