fix: explicitly chain the exception when raising from 'except' block

https://docs.python.org/3/tutorial/errors.html#exception-chaining
https://github.com/adamrehn/ue4cli/pull/65/files/05bd9c77bead5785e8ae6b4ca425f242c90e1ead#r1536831787

ue4cli/JsonDataManager.py

@@ -25,7 +25,7 @@ def loads(self):
 		except json.JSONDecodeError as e:
 			# FIXME: This is the only place outside of Utility class where we use UtilityException.
 			# Not worth to create new Exception class for only one single case, at least not now.
-			raise UtilityException(f'failed to load "{str(path)}" due to: ({type(e).__name__}) {str(e)}')
+			raise UtilityException(f'failed to load "{str(path)}" due to: ({type(e).__name__}) {str(e)}') from e
 
 	def getKey(self, key):
 		"""

ue4cli/UnrealManagerBase.py

@@ -52,7 +52,7 @@ def setEngineRootOverride(self, rootDir):
 		try:
 			self.getEngineVersion()
 		except:
-			raise UnrealManagerException('the specified directory does not appear to contain a valid version of the Unreal Engine.')
+			raise UnrealManagerException('the specified directory does not appear to contain a valid version of the Unreal Engine.') from None
 
 	def clearEngineRootOverride(self):
 		"""
@@ -96,7 +96,7 @@ def getEngineVersion(self, outputFormat = 'full'):
 
 		# Verify that the requested output format is valid
 		if outputFormat not in formats:
-			raise UnrealManagerException('unreconised version output format "{}"'.format(outputFormat))
+			raise UnrealManagerException(f'unreconised version output format "{str(outputFormat)}"')
 
 		return formats[outputFormat]
 
@@ -176,7 +176,7 @@ def getDescriptor(self, dir):
 			try:
 				return self.getPluginDescriptor(dir)
 			except:
-				raise UnrealManagerException('could not detect an Unreal project or plugin in the directory "{}"'.format(dir))
+				raise UnrealManagerException(f'could not detect an Unreal project or plugin in the directory "{str(dir)}"') from None
 
 	def isProject(self, descriptor):
 		"""
@@ -355,11 +355,11 @@ def buildDescriptor(self, dir=os.getcwd(), configuration='Development', target='
 
 		# If the project or plugin is Blueprint-only, there is no C++ code to build
 		if os.path.exists(os.path.join(dir, 'Source')) == False:
-			raise UnrealManagerException('Pure Blueprint {}, nothing to build.'.format(descriptorType))
+			raise UnrealManagerException(f'Pure Blueprint {str(descriptorType)}, nothing to build.')
 
 		# Verify that the specified build configuration is valid
 		if configuration not in self.validBuildConfigurations():
-			raise UnrealManagerException('invalid build configuration "' + configuration + '"')
+			raise UnrealManagerException(f'invalid build configuration "{str(configuration)}"')
 
 		# Check if the user specified the `-notools` flag to opt out of building Engine tools when working with source builds
 		unstripped = list(args)
@@ -408,7 +408,7 @@ def packageProject(self, dir=os.getcwd(), configuration='Shipping', extraArgs=[]
 
 		# Verify that the specified build configuration is valid
 		if configuration not in self.validBuildConfigurations():
-			raise UnrealManagerException('invalid build configuration "' + configuration + '"')
+			raise UnrealManagerException(f'invalid build configuration "{str(configuration)}"')
 
 		# Strip out the `-NoCompileEditor` flag if the user has specified it, since the Development version
 		# of the Editor modules for the project are needed in order to run the commandlet that cooks content
@@ -538,10 +538,12 @@ def listAutomationTests(self, projectFile):
 		# Detect if the Editor terminated abnormally (i.e. not triggered by `automation quit`)
 		# In Unreal Engine 4.27.0, the exit method changed from RequestExit to RequestExitWithStatus
 		if 'PlatformMisc::RequestExit(' not in logOutput.stdout and 'PlatformMisc::RequestExitWithStatus(' not in logOutput.stdout:
-			raise UnrealManagerException(
-				'failed to retrieve the list of automation tests!' +
-				' stdout was: "{}", stderr was: "{}"'.format(logOutput.stdout, logOutput.stderr)
-			)
+			Utility.printStderr("Warning: abnormal Editor termination detected!")
+			Utility.printStderr("printing stdout..")
+			print(logOutput.stdout)
+			Utility.printStderr("printing stderr..")
+			print(logOutput.stderr)
+			raise UnrealManagerException('failed to retrieve the list of automation tests!')
 
 		return sorted(list(tests))
 

ue4cli/Utility.py

@@ -33,7 +33,7 @@ def readFile(filename):
 			with open(filename, 'rb') as f:
 				return f.read().decode('utf-8')
 		except OSError as e:
-			raise UtilityException(f'failed to read file "{str(filename)}" due to: ({type(e).__name__}) {str(e)}')
+			raise UtilityException(f'failed to read file "{str(filename)}" due to: ({type(e).__name__}) {str(e)}') from e
 
 	@staticmethod
 	def writeFile(filename, data):
@@ -44,7 +44,7 @@ def writeFile(filename, data):
 			with open(filename, 'wb') as f:
 				f.write(data.encode('utf-8'))
 		except OSError as e:
-			raise UtilityException(f'failed to write file "{str(filename)}" due to: ({type(e).__name__}) {str(e)}')
+			raise UtilityException(f'failed to write file "{str(filename)}" due to: ({type(e).__name__}) {str(e)}') from e
 
 	@staticmethod
 	def moveFile(src, dst):
@@ -54,7 +54,7 @@ def moveFile(src, dst):
 		try:
 			shutil.move(src, dst)
 		except OSError as e:
-			raise UtilityException(f'failed to move file from "{str(src)}" to "{str(dst)}" due to: ({type(e).__name__}) {str(e)}')
+			raise UtilityException(f'failed to move file from "{str(src)}" to "{str(dst)}" due to: ({type(e).__name__}) {str(e)}') from e
 
 	@staticmethod
 	def patchFile(filename, replacements):
@@ -77,7 +77,7 @@ def removeDir(path, ignore_errors=False):
 		try:
 			shutil.rmtree(path, ignore_errors)
 		except OSError as e:
-			raise UtilityException(f'failed to remove directory "{str(path)}" due to: ({type(e).__name__}) {str(e)}')
+			raise UtilityException(f'failed to remove directory "{str(path)}" due to: ({type(e).__name__}) {str(e)}') from e
 
 	@staticmethod
 	def makeDirs(name, mode=0o777, exist_ok=False):
@@ -87,7 +87,7 @@ def makeDirs(name, mode=0o777, exist_ok=False):
 		try:
 			os.makedirs(name, mode, exist_ok)
 		except OSError as e:
-			raise UtilityException(f'failed to create directory "{str(name)}" due to: ({type(e).__name__}) {str(e)}')
+			raise UtilityException(f'failed to create directory "{str(name)}" due to: ({type(e).__name__}) {str(e)}') from e
 
 	@staticmethod
 	def forwardSlashes(paths):

ue4cli/cli.py

@@ -227,7 +227,7 @@ def main():
 		else:
 			# FIXME: This is the only place outside of UnrealManager... classes where we use UnrealManagerException.
 			# Not worth to create new Exception class for only one single case, at least not now.
-			raise UnrealManagerException('unrecognised command "' + command + '"')
+			raise UnrealManagerException(f'unrecognised command "{str(command)}"') from None
 
 	except (
 			UnrealManagerException,