Raise exceptions and trap errors properly

redfish-finder, when it encounters should be using the normal python exception
model to handle errors, update it to do so

This also corrects some erroneous behavior in which odd errors are returned on
systems not supporting redfish

Singed-off-by: Neil Horman <nhorman@tuxriver.com>

Author: Neil Horman

redfish-finder

@@ -69,7 +69,7 @@ class USBNetDevice(NetDevice):
 
 		# Now we need to find the corresponding device name in sysfs
 		if self._find_device() == False:
-			return None
+			raise RuntimeError("Unable to find USB network device")
 
 	def _getname(self, dpath):
 		for root, dirs, files in os.walk(dpath, topdown=False):
@@ -122,8 +122,7 @@ class HostConfig():
 		try:
 			cursor = cursor_consume_next(cursor, "Host IP Assignment Type: ")
 			if cursor == None:
-				printf("redfish-finder: Unable to parse SMBIOS Host IP Assignment Type")
-				return None
+				raise RuntimeError("redfish-finder: Unable to parse SMBIOS Host IP Assignment Type")
 			if cursor.split()[0] == "Static":
 				self.assigntype = []
 				self.assigntype.append(AssignType.STATIC)
@@ -151,11 +150,9 @@ class HostConfig():
 				self.network.append(0)
 			else:
 				# Support the other types later
-				print("redfish-finder: Unable to parse SMBIOS Host configuaration")
-				return None
+				raise RuntimeError("redfish-finder: Unable to parse SMBIOS Host configuaration")
 		except:
-			print("redfish-finder: Unexpected error while parsing HostConfig!")
-			return None
+			raise RuntimeError("redfish-finder: Unexpected error while parsing HostConfig!")
 
 	def merge(self, newconfig):
 		self.assigntype.extend(newconfig.assigntype)
@@ -209,8 +206,7 @@ class ServiceConfig():
 		try:
 			cursor = cursor_consume_next(cursor, "Redfish Service IP Discovery Type: ")
 			if cursor == None:
-				print("redfish-finder: Unable to find Redfish Service Info")
-				return None
+				raise RuntimeError("redfish-finder: Unable to find Redfish Service Info")
 			if cursor.split()[0] == "Static":
 				self.assigntype = AssignType.STATIC
 				cursor = cursor_consume_next(cursor, "Redfish Service IP Address Format: ")
@@ -246,7 +242,7 @@ class ServiceConfig():
 			else:
 				self.hostname = ""
 		except:
-			print("redfish-finder: Unexpected error parsing ServiceConfig")
+			raise RuntimeError("redfish-finder: Unexpected error parsing ServiceConfig")
 
 	def merge(self, newconfig):
 		self.address.extend(newconfig.address)
@@ -272,12 +268,14 @@ class dmiobject():
 		cursor = dmioutput
 		# Find the type 42 header, if not found, nothing to do here
 		cursor = cursor_consume_next(cursor, "Management Controller Host Interface\n")
+		if cursor == None:
+			raise RuntimeError("Unable to find Management Controller Host Interface block in SMBIOS")
 		while (cursor != None):
 			if (cursor == None):
-				return None
+				raise RuntimeError("No Redfish Host support detected")
 			cursor = cursor_consume_next(cursor, "Host Interface Type: Network\n")
 			if (cursor == None):
-				return None
+				raise RuntimeError("No supported Redfish host interface type found")
 
 			# If we get here then we know this is a network interface device
 			cursor = cursor_consume_next(cursor, "Device Type: ")
@@ -290,9 +288,6 @@ class dmiobject():
 			if (dtype == "USB"):
 				newdev = USBNetDevice(cursor)
 
-			if newdev == None:
-				return None
-
 			if self.device == None:
 				self.device = newdev
 			else:
@@ -301,21 +296,16 @@ class dmiobject():
 			# Now find the Redfish over IP section
 			cursor = cursor_consume_next(cursor, "Protocol ID: 04 (Redfish over IP)\n")
 			if (cursor == None):
-				print("redfish-finder: Unable to find Redfish Protocol")
-				return None
+				raise RuntimeError("No Redfish over IP Protocol support")
 
 			newhostconfig = HostConfig(cursor)
-			if newhostconfig == None:
-				return None
 
 			if self.hostconfig == None:
 				self.hostconfig = newhostconfig
 			else:
 				self.hostconfig.merge(newhostconfig)
 
 			serviceconfig = ServiceConfig(cursor)
-			if serviceconfig == None:
-				return None
 
 			if self.serviceconfig == None:
 				self.serviceconfig = serviceconfig
@@ -417,8 +407,7 @@ class nmConnection():
 				subprocess.check_call(create)
 				propstr = subprocess.check_output(["nmcli", "con", "show", ifc.getifcname()])
 			except:
-				print("redfish-finder: Unexpected error building connection to %s" % self.ifc)
-				return None
+				raise RuntimeError("redfish-finder: Unexpected error building connection to %s" % self.ifc)
 
 		try:
 			self.properties = {}
@@ -430,8 +419,7 @@ class nmConnection():
 					continue
 				self.properties[la[0].strip(":")] = la[1]
 		except:
-			print("Unexpected error parsing connection for %s" % self.ifc)
-			return None
+			raise RuntimeError("Unexpected error parsing connection for %s" % self.ifc)
 
 	#
 	# Update a property value in this network manager object
@@ -491,7 +479,10 @@ class nmConnection():
 		return str(self.properties)
 
 def get_info_from_dmidecode():
-	dmioutput = subprocess.check_output(["/usr/sbin/dmidecode", "-t42"])
+	try:
+		dmioutput = subprocess.check_output(["/usr/sbin/dmidecode", "-t42"])
+	except:
+		raise RuntimeError("Failed to run dmidecode.  Make sure you run as root")
 	return dmiobject(dmioutput.decode())
 
 def main():
@@ -500,13 +491,19 @@ def main():
 	args = parser.parse_args(sys.argv[1:])
 
 	print("redfish-finder: Getting dmidecode info")
-	smbios_info = get_info_from_dmidecode()
-	if smbios_info == None:
+	try:
+		smbios_info = get_info_from_dmidecode()
+	except RuntimeError as e:
+		print("Error parsing dmidecode information: %s\n" % e)
 		sys.exit(1)
+
 	print("redfish-finder: Building NetworkManager connection info")
-	conn = nmConnection(smbios_info.device)
-	if conn == None:
+	try:
+		conn = nmConnection(smbios_info.device)
+	except RuntimeError as e:
+		print("redfish-finder: Error building nm connection: %s\n" % e)
 		sys.exit(1)
+
 	print("redfish-finder: Obtaining OS config info")
 	svc = OSServiceData(smbios_info.serviceconfig)
 	if svc == None: