Don't silently swallow exceptions in python context managers

Notably this causes processing modules to silently fail to load
without any warnings if the required dependancies (such as pyscopg2)
are not installed

(cherry picked from commit 1040fe8)

python/core/additions/projectdirtyblocker.py

@@ -44,4 +44,4 @@ def __enter__(self):
 
     def __exit__(self, ex_type, ex_value, traceback):
         del self.blocker
-        return True
+        return ex_type is None

python/core/additions/readwritecontextentercategory.py

@@ -43,4 +43,4 @@ def __enter__(self):
 
     def __exit__(self, ex_type, ex_value, traceback):
         del self.popper
-        return True
+        return ex_type is None

python/core/additions/runtimeprofiler.py

@@ -43,4 +43,4 @@ def __enter__(self):
 
     def __exit__(self, ex_type, ex_value, traceback):
         del self.profiler
-        return True
+        return ex_type is None

python/plugins/db_manager/db_plugins/vlayers/connector.py

@@ -45,8 +45,9 @@ def __init__(self, sqlite_file):
     def __enter__(self):
         return self.conn
 
-    def __exit__(self, type, value, traceback):
+    def __exit__(self, ex_type, value, traceback):
         self.conn.close()
+        return ex_type is None
 
 
 def getQueryGeometryName(sqlite_file):

python/utils.py

@@ -710,6 +710,7 @@ def __enter__(self):
 
     def __exit__(self, exc_type, exc_val, exc_tb):
         QApplication.restoreOverrideCursor()
+        return exc_type is None
 
 
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