Nimble install stops prematurely when asked to not overwrite existing package install
today i performed the command `nimble install lua luna` and was prompted to overwrite the existing install of `lua@1.0` to which i input `n` and discovered that nimble exited and i was returned to my shell prompt without it attempting to install the second package listed, `luna`. I tried this on both linux (ubuntu 18.04.4) and windows 10 (10.0.18363 N/A Build 18363) and get the same results. 

first attempt (saying `no` to overwrite prompt):
```
$ nimble install lua luna
Downloading https://github.com/nim-lang/lua using git
   Warning: Package 'lua' has an incorrect structure. The top level of the package source directory should contain at most one module, named 'lua.nim', but a file named 'lauxlib.nim' was found. This will be an error in the future.
      Hint: If this is the primary source file in the package, rename it to 'lua.nim'. If it's a source file required by the main module, or if it is one of several modules exposed by 'lua', then move it into a 'lua/' subdirectory. If it's a test file or otherwise not required to build the the package 'lua.nim', prevent its installation by adding `skipFiles = @["lauxlib.nim"]` to the .nimble file. See https://github.com/nim-lang/nimble#libraries for more info.
  Verifying dependencies for lua@1.0
 Installing lua@1.0
    Prompt: lua@1.0 already exists. Overwrite? [y/N]
    Answer: n
$
```

second attempt (saying `yes` to first overwrite prompt):
```
$ nimble install lua luna 
Downloading https://github.com/nim-lang/lua using git
   Warning: Package 'lua' has an incorrect structure. The top level of the package source directory should contain at most one module, named 'lua.nim', but a file named 'lauxlib.nim' was found. This will be an error in the future.
      Hint: If this is the primary source file in the package, rename it to 'lua.nim'. If it's a source file required by the main module, or if it is one of several modules exposed by 'lua', then move it into a 'lua/' subdirectory. If it's a test file or otherwise not required to build the the package 'lua.nim', prevent its installation by adding `skipFiles = @["lauxlib.nim"]` to the .nimble file. See https://github.com/nim-lang/nimble#libraries for more info.
  Verifying dependencies for lua@1.0
 Installing lua@1.0
    Prompt: lua@1.0 already exists. Overwrite? [y/N]
    Answer: y
   Success: lua installed successfully.
Downloading https://github.com/smallfx/luna.nim using git
  Verifying dependencies for luna@0.1.0
 Installing luna@0.1.0
    Prompt: luna@0.1.0 already exists. Overwrite? [y/N]
    Answer: n
$ 
```
---

the version of `nimble` i am currently using:
```
nimble v0.11.0 compiled at 2020-03-11 21:40:19
git hash: 5bb795a364a431f897c3864186dbe1aa138c85b9
```
and it was compiled against `nim` version:
```
Nim Compiler Version 1.0.6 [Linux: amd64]
Compiled at 2020-01-23
Copyright (c) 2006-2019 by Andreas Rumpf

git hash: 89b39ee8fe271d0e1b75c15a4c6cf82eb9c13aea
active boot switches: -d:release
```