Work around change to exception type from lock in 1.2

In Julia 1.2, the error that occurs when releasing a semaphore with
mismatched release/acquire counts is now an ErrorException, whereas
previously it was an AssertionError.

See JuliaLang/julia#30061

test/runtests.jl

@@ -23,9 +23,17 @@ include("utils.jl")
         @test "Expected error but no error thrown" == nothing
     catch err
         @test err isa RemoteException
-        @test err.captured.ex isa AssertionError
 
-        if !isa(err, RemoteException) || !isa(err.captured.ex, AssertionError)
+        if VERSION >= v"1.2.0-DEV.28"
+            expected = ErrorException
+            @test err.captured.ex isa expected
+            @test occursin("release count must match acquire count", err.captured.ex.msg)
+        else
+            expected = AssertionError
+            @test err.captured.ex isa expected
+        end
+
+        if !isa(err, RemoteException) || !isa(err.captured.ex, expected)
             rethrow(err)
         end
     end
@@ -80,9 +88,17 @@ end
             @test "Expected error but no error thrown" == nothing
         catch err
             @test err isa RemoteException
-            @test err.captured.ex isa AssertionError
 
-            if !isa(err, RemoteException) || !isa(err.captured.ex, AssertionError)
+            if VERSION >= v"1.2.0-DEV.28"
+                expected = ErrorException
+                @test err.captured.ex isa expected
+                @test occursin("release count must match acquire count", err.captured.ex.msg)
+            else
+                expected = AssertionError
+                @test err.captured.ex isa expected
+            end
+
+            if !isa(err, RemoteException) || !isa(err.captured.ex, expected)
                 rethrow(err)
             end
         end