flycheck two pytests (#1294)

@mmatera I was trying to add a test for `HoldForm[Times[x]] == Times[x]`
of a recent PR of yours (from a while ago) but haven't been able to
figure out how to do. in the process, I have this lint stuff from the
tests.

---------

Co-authored-by: Juan Mauricio Matera <matera@fisica.unlp.edu.ar>

Author: rocky

mathics/builtin/arithfns/basic.py

@@ -287,16 +287,16 @@ def format_plus(self, items, evaluation):
         "Plus[items__]"
 
         def negate(item):  # -> Expression (see FIXME below)
-            if item.has_form("Times", 1, None):
+            if item.has_form("Times", 2, None):
                 if isinstance(item.elements[0], Number):
-                    neg = -item.elements[0]
-                    if neg.sameQ(Integer1):
-                        if len(item.elements) == 1:
-                            return neg
-                        else:
-                            return Expression(SymbolTimes, *item.elements[1:])
-                    else:
-                        return Expression(SymbolTimes, neg, *item.elements[1:])
+                    first, *rest = item.elements
+                    first = -first
+                    if first.sameQ(Integer1):
+                        if len(rest) == 1:
+                            return rest[0]
+                        return Expression(SymbolTimes, *rest)
+
+                    return Expression(SymbolTimes, first, *rest)
                 else:
                     return Expression(SymbolTimes, IntegerM1, *item.elements)
             elif isinstance(item, Number):
@@ -632,6 +632,8 @@ def inverse(item):
                 return item
 
         items = items.get_sequence()
+        if len(items) < 2:
+            return
         positive = []
         negative = []
         for item in items:

test/builtin/arithmetic/test_basic.py

@@ -109,6 +109,16 @@ def test_exponential(str_expr, str_expected):
             "ComplexInfinity",
             "Goes to the previous case because of the rule in Power",
         ),
+        (
+            "HoldForm[Times[]]",
+            "Times[]",
+            "Times without arguments is not formatted",
+        ),
+        (
+            "HoldForm[Times[x]]",
+            "Times[x]",
+            "Times with a single argument is not formatted",
+        ),
     ],
 )
 def test_multiply(str_expr, str_expected, msg):

test/builtin/test_evaluation.py

@@ -5,7 +5,7 @@
 
 
 import sys
-from test.helper import check_evaluation_as_in_cli, session
+from test.helper import check_evaluation_as_in_cli
 
 import pytest
 

test/core/convert/test_sympy.py

@@ -12,19 +12,13 @@
     Integer2,
     Integer3,
     IntegerM1,
-    MachineReal,
-    PrecisionReal,
     Rational,
-    RationalOneHalf,
     Real,
     String,
 )
 from mathics.core.convert.sympy import from_sympy, sympy_singleton_to_mathics
 from mathics.core.expression import Expression
-from mathics.core.expression_predefined import (
-    MATHICS3_COMPLEX_INFINITY,
-    MATHICS3_INFINITY,
-)
+from mathics.core.expression_predefined import MATHICS3_COMPLEX_INFINITY
 from mathics.core.symbols import (
     Symbol,
     SymbolFalse,
@@ -34,18 +28,7 @@
     SymbolTimes,
     SymbolTrue,
 )
-from mathics.core.systemsymbols import (
-    SymbolAnd,
-    SymbolComplexInfinity,
-    SymbolDirectedInfinity,
-    SymbolE,
-    SymbolExp,
-    SymbolI,
-    SymbolIndeterminate,
-    SymbolInfinity,
-    SymbolPi,
-    SymbolSin,
-)
+from mathics.core.systemsymbols import SymbolE, SymbolExp, SymbolI, SymbolPi, SymbolSin
 
 Symbol_a = Symbol("Global`a")
 Symbol_b = Symbol("Global`b")