flake8 fixes - exception handling changed

flake was flagging the bare except: expression.  From testing, it
looks like that exception handler only gets ValueError. So changed it
to

  except ValueError:

and added an

   except BaseExpression

that just re-raises the exception. But I think this better expresses
the expected flow.

Author: rouilj

roundup/mlink_expr.py

@@ -1,7 +1,7 @@
 #
 # Copyright: 2010 Intevation GmbH.
 #            2021 Ralf Schlatterbeck, [email protected].
-# 
+#
 
 # This module is Free Software under the Roundup licensing,
 # see the COPYING.txt file coming with Roundup.
@@ -17,6 +17,7 @@ def visit(self, visitor):
         self.x.visit(visitor)
         self.y.visit(visitor)
 
+
 class Unary:
 
     def __init__(self, x):
@@ -28,6 +29,7 @@ def generate(self, atom):
     def visit(self, visitor):
         self.x.visit(visitor)
 
+
 class Equals(Unary):
 
     def evaluate(self, v):
@@ -36,6 +38,7 @@ def evaluate(self, v):
     def visit(self, visitor):
         visitor(self)
 
+
 class Empty(Unary):
 
     def evaluate(self, v):
@@ -44,6 +47,7 @@ def evaluate(self, v):
     def visit(self, visitor):
         visitor(self)
 
+
 class Not(Unary):
 
     def evaluate(self, v):
@@ -52,6 +56,7 @@ def evaluate(self, v):
     def generate(self, atom):
         return "NOT(%s)" % self.x.generate(atom)
 
+
 class Or(Binary):
 
     def evaluate(self, v):
@@ -62,6 +67,7 @@ def generate(self, atom):
             self.x.generate(atom),
             self.y.generate(atom))
 
+
 class And(Binary):
 
     def evaluate(self, v):
@@ -72,19 +78,21 @@ def generate(self, atom):
             self.x.generate(atom),
             self.y.generate(atom))
 
+
 def compile_expression(opcodes):
 
     stack = []
     push, pop = stack.append, stack.pop
     for opcode in opcodes:
-        if   opcode == -1: push(Empty(opcode))
-        elif opcode == -2: push(Not(pop()))
-        elif opcode == -3: push(And(pop(), pop()))
-        elif opcode == -4: push(Or(pop(), pop()))
-        else:              push(Equals(opcode))
+        if   opcode == -1: push(Empty(opcode))      # noqa: E271,E701
+        elif opcode == -2: push(Not(pop()))         # noqa: E701
+        elif opcode == -3: push(And(pop(), pop()))  # noqa: E701
+        elif opcode == -4: push(Or(pop(), pop()))   # noqa: E701
+        else:              push(Equals(opcode))     # noqa: E701
 
     return pop()
 
+
 class Expression:
 
     def __init__(self, v, is_link=False):
@@ -99,7 +107,7 @@ def __init__(self, v, is_link=False):
                     x and [int(x)] or [])
             else:
                 self.evaluate = lambda x: compiled.evaluate([int(y) for y in x])
-        except:
+        except ValueError:
             if is_link:
                 v = [None if x == '-1' else x for x in v]
                 self.evaluate = lambda x: x in v
@@ -108,3 +116,5 @@ def __init__(self, v, is_link=False):
                 self.evaluate = lambda x: bool(set(x) & set(v)) or not x
             else:
                 self.evaluate = lambda x: bool(set(x) & set(v))
+        except BaseException:
+            raise