Let a failed request report itself

Two places where the code that exists to explain a failure fails instead, and
the caller is shown the second failure rather than the first.

_do_web_request builds its message from the response body when that body is
not the JSON error document the spec asks for. An html 404 page is exactly
that, the body is bytes, and str + bytes raised TypeError. The status and the
body never reached anyone.

LenovoFirmwareConfig raised a bare Exception when python-lxml and
python-eficompressor are absent. Confluent has no handler for one, so a
missing dependency showed as "Unexpected Error" and hid a message that
already said what to install.

Neither changes what fails, only what the caller is told.

confluent_server/aiohmi/ipmi/oem/lenovo/config.py

@@ -147,8 +147,12 @@ def _eval_conditional(expression, cfg, setting):
 class LenovoFirmwareConfig(object):
     def __init__(self, xc, useipmi=True):
         if not etree:
-            raise Exception("python-lxml and python-eficompressor required "
-                            "for this function")
+            # Not a bare Exception. Confluent has no handler for one, so a
+            # missing optional dependency showed as "Unexpected Error" and hid
+            # the message below, which already names what to install.
+            raise pygexc.UnsupportedFunctionality(
+                "python-lxml and python-eficompressor required "
+                "for this function")
         if useipmi:
             self.connection = xc.ipmicmd
         else:

confluent_server/aiohmi/redfish/oem/generic.py

@@ -1794,7 +1794,14 @@ class OEMHandler(object):
                 errmsg = ','.join(errmsg)
                 raise exc.RedfishError(errmsg)
             except (ValueError, KeyError):
-                raise exc.PyghmiException(str(url) + ":" + res[0])
+                # Reached by an html 404 page, or anything else that is not
+                # the JSON error document. res[0] is bytes there, so building
+                # the message crashed and the caller saw that TypeError
+                # instead of the status and the body.
+                body = res[0]
+                if isinstance(body, bytes):
+                    body = body.decode('utf-8', errors='replace')
+                raise exc.PyghmiException('{0}:{1}'.format(url, body))
         if payload is None and method is None:
             self._urlcache[url] = {
                 'contents': res[0],