[modules] Improve error messages.

src/messages.h

Index: src/messages.h
diff --git a/src/messages.h b/src/messages.h
index b3e55cac226086e68d6ca1f3f6fe96913bee0884..3a03de9ce2a2eb76c666736bbd044cbc34944625 100644
--- a/src/messages.h
+++ b/src/messages.h
@@ -520,7 +520,8 @@ class ErrorUtils : public AllStatic {
   T(UnsupportedTimeZone, "Unsupported time zone specified %")                  \
   T(ValueOutOfRange, "Value % out of range for % options property %")          \
   /* SyntaxError */                                                            \
-  T(AmbiguousExport, "Multiple star exports provide name '%'")                 \
+  T(AmbiguousExport,                                                           \
+    "The requested module contains conflicting star exports for name '%'")     \
   T(BadGetterArity, "Getter must not have any formal parameters.")             \
   T(BadSetterArity, "Setter must have exactly one formal parameter.")          \
   T(ConstructorIsAccessor, "Class constructor may not be an accessor")         \
@@ -625,7 +626,8 @@ class ErrorUtils : public AllStatic {
   T(UnexpectedTokenString, "Unexpected string")                                \
   T(UnexpectedTokenRegExp, "Unexpected regular expression")                    \
   T(UnknownLabel, "Undefined label '%'")                                       \
-  T(UnresolvableExport, "Module does not provide an export named '%'")         \
+  T(UnresolvableExport,                                                        \
+    "The requested module does not provide an export named '%'")               \
   T(UnterminatedArgList, "missing ) after argument list")                      \
   T(UnterminatedRegExp, "Invalid regular expression: missing /")               \
   T(UnterminatedTemplate, "Unterminated template literal")                     \