Uninstall dependents doesn't work
Today I tried installing `nim-chronicles` only to find that it didn't fit my need. I went to uninstall it and all of its dependents but found that it didn't worK

```sh
~/D/P/R/viroid-search ❯❯❯ nimble list -i                                                                                       (viroid-search)
argparse  [0.10.1]
docopt  [0.6.7]
librtd  [0.0.2.1, 0.0.2.2]
nimpy  [0.1.1, 0.1.0]
progress  [1.1.1]
viroid_search  [#head]
~/D/P/R/viroid-search ❯❯❯ nimble install chronicles                                                                            (viroid-search)
Downloading https://github.com/status-im/nim-chronicles using git
  Verifying dependencies for chronicles@0.10.0
 Installing testutils@any version
Downloading https://github.com/status-im/nim-testutils using git
  Verifying dependencies for testutils@0.3.0
 Installing testutils@0.3.0
   Building testutils/ntu using c backend
/private/var/folders/gw/sk03t1cn3wlgclyc55yst44w0000gn/T/nimble_73660/githubcom_statusimnimtestutils/testutils/fuzzing_engines.nim(1, 19) Warning: import os.nim instead; ospaths is deprecated [Deprecated]
/private/var/folders/gw/sk03t1cn3wlgclyc55yst44w0000gn/T/nimble_73660/githubcom_statusimnimtestutils/ntu.nim(64, 15) template/generic instantiation of `styledEcho` from here
/usr/local/Cellar/nim/1.4.0/nim/lib/pure/terminal.nim(744, 9) template/generic instantiation of `styledWriteLine` from here
/private/var/folders/gw/sk03t1cn3wlgclyc55yst44w0000gn/T/nimble_73660/githubcom_statusimnimtestutils/ntu.nim(65, 33) Warning: binary is deprecated [Deprecated]
/private/var/folders/gw/sk03t1cn3wlgclyc55yst44w0000gn/T/nimble_73660/githubcom_statusimnimtestutils/ntu.nim(136, 14) Warning: use fileExists; existsFile is deprecated [Deprecated]
/private/var/folders/gw/sk03t1cn3wlgclyc55yst44w0000gn/T/nimble_73660/githubcom_statusimnimtestutils/ntu.nim(167, 12) Warning: use fileExists; existsFile is deprecated [Deprecated]
/private/var/folders/gw/sk03t1cn3wlgclyc55yst44w0000gn/T/nimble_73660/githubcom_statusimnimtestutils/ntu.nim(240, 16) Warning: binary is deprecated [Deprecated]
/private/var/folders/gw/sk03t1cn3wlgclyc55yst44w0000gn/T/nimble_73660/githubcom_statusimnimtestutils/testutils/config.nim(125, 18) Warning: Potential object case transition, instantiate new object instead [CaseTransition]
   Success: testutils installed successfully.
 Installing json_serialization@any version
Downloading https://github.com/status-im/nim-json-serialization using git
  Verifying dependencies for json_serialization@0.1.0
 Installing serialization@any version
Downloading https://github.com/status-im/nim-serialization using git
  Verifying dependencies for serialization@0.1.0
 Installing faststreams@any version
Downloading https://github.com/status-im/nim-faststreams using git
  Verifying dependencies for faststreams@0.2.0
 Installing stew@any version
Downloading https://github.com/status-im/nim-stew using git
  Verifying dependencies for stew@0.1.0
 Installing stew@0.1.0
   Success: stew installed successfully.
      Info: Dependency on testutils@any version already satisfied
  Verifying dependencies for testutils@0.3.0
 Installing chronos@any version
Downloading https://github.com/status-im/nim-chronos using git
  Verifying dependencies for chronos@2.5.2
      Info: Dependency on stew@any version already satisfied
  Verifying dependencies for stew@0.1.0
 Installing bearssl@any version
Downloading https://github.com/status-im/nim-bearssl using git
  Verifying dependencies for bearssl@0.1.5
 Installing bearssl@0.1.5
   Success: bearssl installed successfully.
 Installing chronos@2.5.2
   Success: chronos installed successfully.
 Installing faststreams@0.2.0
   Success: faststreams installed successfully.
      Info: Dependency on stew@any version already satisfied
  Verifying dependencies for stew@0.1.0
 Installing serialization@0.1.0
   Success: serialization installed successfully.
      Info: Dependency on stew@any version already satisfied
  Verifying dependencies for stew@0.1.0
 Installing json_serialization@0.1.0
   Success: json_serialization installed successfully.
 Installing chronicles@0.10.0
   Success: chronicles installed successfully.
~/D/P/R/viroid-search ❯❯❯ nimble uninstall -i chronicles                                                                       (viroid-search)
    Looking for chronicles (any version)
   Checking reverse dependencies
    Prompt: The following packages will be removed:
  chronicles (0.10.0)
Do you wish to continue? [y/N]
    Answer: y
    Removed chronicles (0.10.0)
~/D/P/R/viroid-search ❯❯❯ nimble list -i                                                                                       (viroid-search)
argparse  [0.10.1]
bearssl  [0.1.5]
chronos  [2.5.2]
docopt  [0.6.7]
faststreams  [0.2.0]
json_serialization  [0.1.0]
librtd  [0.0.2.1, 0.0.2.2]
nimpy  [0.1.1, 0.1.0]
progress  [1.1.1]
serialization  [0.1.0]
stew  [0.1.0]
testutils  [0.3.0]
viroid_search  [#head]
```

Nimble info:

```
nimble v0.12.0 compiled at 2020-10-17 06:31:40
git hash: 8f7af860c5ce9634af880a7081c6435e1f2a5148
```