Repository: spack/spack

Issue:
Installation issue: syscalc fails with ChecksumError
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### Steps to reproduce the issue

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```console
$ spack install syscalc
```

yields

```
==> Installing syscalc
==> No binary for syscalc found: installing from source
==> Fetching http://madgraph.phys.ucl.ac.be/Downloads/SysCalc_V1.1.7.tar.gz
######################################################################## 100.0%
==> Error: ChecksumError: sha256 checksum failed for /tmp/root/spack-stage/spack-stage-syscalc-1.1.7-zlus4tseqby2qpwa2wnan23c5kvgwnif/SysCalc_V1.1.7.tar.gz
    Expected d33219a525a54733bdfd02d8314288bdecd977fb1e97ddeaf13bf470bbbdd386 but got 5b06f4955508f7c59660fa632ede9265d8f2ca7d9cd87f145a083da74e54602f

/spack/lib/spack/spack/package.py:1266, in do_fetch:
       1263        self.stage.fetch(mirror_only, err_msg=err_msg)
       1264        self._fetch_time = time.time() - start_time
       1265
  >>   1266        if checksum and self.version in self.versions:
       1267            self.stage.check()
       1268
       1269        self.stage.cache_local()
```

### Information on your system

<!-- Please include the output of `spack debug report` -->
```
$ spack debug report
* **Spack:** 0.15.4-1462-383b5b7
* **Python:** 2.7.5
* **Platform:** linux-centos7-skylake
```

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### Additional information

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It seems that that the file that is found at the location specified by the package:
https://github.com/spack/spack/blob/e4c1cb380beb088393e47ba9caa27a2e5953b4db/var/spack/repos/builtin/packages/syscalc/package.py#L13-L15

has changed, as directly downloading it and running
```
$ sha256sum SysCalc_V1.1.7.tar.gz 
5b06f4955508f7c59660fa632ede9265d8f2ca7d9cd87f145a083da74e54602f  SysCalc_V1.1.7.tar.gz
```

does not yield the expected checksum.

`spack maintainers syscalc` doesn't yield anything, so I am paging @iarspider here, which is the only one that turned up for syscalc using `git blame`.

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### General information

<!-- These boxes can be checked by replacing [ ] with [x] or by clicking them after submitting the issue. -->
- [x] I have run `spack debug report` and reported the version of Spack/Python/Platform
- [x] I have run `spack maintainers <name-of-the-package>` and @mentioned any maintainers
- [ ] I have uploaded the build log and environment files
- [x] I have searched the issues of this repo and believe this is not a duplicate



Discussion:

Resolving patch:
diff --git a/var/spack/repos/builtin/packages/syscalc/package.py b/var/spack/repos/builtin/packages/syscalc/package.py
--- a/var/spack/repos/builtin/packages/syscalc/package.py
+++ b/var/spack/repos/builtin/packages/syscalc/package.py
@@ -10,9 +10,10 @@ class Syscalc(MakefilePackage):
     """ A tool to derive theoretical systematic uncertainties"""
 
     homepage = "https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/SysCalc"
-    url      = "http://madgraph.phys.ucl.ac.be/Downloads/SysCalc_V1.1.7.tar.gz"
+    url      = "https://bazaar.launchpad.net/~mgtools/mg5amcnlo/SysCalc/tarball/17"
 
-    version('1.1.7', sha256='d33219a525a54733bdfd02d8314288bdecd977fb1e97ddeaf13bf470bbbdd386')
+    version('1.1.7', sha256='ac73df0f9f195eb62601fafc2eede3db17a562750f7971616870d6df4abd1b6c',
+            url='https://bazaar.launchpad.net/~mgtools/mg5amcnlo/SysCalc/tarball/17')
 
     depends_on('lhapdf@6:')
 


Test patch: